Paper cash started replacing precious metals many, many centuries ago. However, it took PayPal’s Venmo (PYPL) just eight years to supplant cash for millions of people—largely millennials—looking to pay each other for things or split a restaurant tab.

“We are in a period of profound transformation in the very nature of money,” Venmo’s Josh Criscoe, head of corporate affairs, told Yahoo Finance. “Digital payments are quickly replacing cash and Venmo has been front-and-center within this shift.” Likely sensing Venmo’s momentum, PayPal acquired Venmo from Braintree for $800 million in 2013.

In the last quarter, Venmo processed $8 billion in payments and is still growing significantly, jumping 103% over last year in transaction volume. The lack of public payment volume data for competitors—Square (SQ), for instance, does not release payment volume for its service Square Cash—suggests that Venmo is leading the industry.

But even more compelling than that suggestion is the fact that “to Venmo” has entered the lexicon as a verb in a way few companies other than Uber and Google have experienced. (“Venmo me $12 for those beers”).

Venmo’s success is directly tied to this social component, and not simply because 30% of payments are described with at least one emoji. According to Criscoe, the majority of Venmo’s growth has been word of mouth.

“Venmo invented social payments and we’ve been the leader in the space ever since,” Crisco said.

The big banks want a taste

The big banks have banded together and have their own service now, Zelle, which they hope will give them a taste of what has the potential to be an absolutely colossal industry.

Zelle has actually been around since 2011 in some iteration. Between 2011 and 2014, a consortium of six big banks banded together—Bank of America, Capital One, JPMorgan Chase, US Bank, Wells Fargo—to create their own payment system called clearXchange.

Eventually snowballing into a consortium of 34 heavy-hitting partners of the banking world, clearXchange could not chalk up a win against Venmo in the payments wars. The banks shrunk back to their corner and emerged in June, officially rebranding clearXchange as “Zelle.” Users can use Zelle to pay each other from inside their bank’s app.

The big banks’ Zelle has an extremely tough path to success, considering Venmo’s strong footing in the industry. According to a new poll from LendEDU, 93.9% of Venmo users have never heard of Zelle and 88.1% of the 500 Venmo users polled do not know what it is.

Putting aside Zelle’s lack of visibility, LendEDU explained that it was a payment network launched by banks and asked people if they would consider trying it. By a two-to-one ratio, people said no. Considering Venmo’s dominance and growth, this is not auspicious for Wall Street.

Tech companies have also had little success with their own payment systems

Today many marquee tech companies have followed Venmo’s lead and rolled out peer-to-peer payment services. In a tech landscape in which everything is a chat app and everything is video, everything is also payments.

Facebook (FB) has Payments in its Messenger services, launched in 2015. Google’s (GOOG) Gmail began to allow Android users to request and send money earlier this year. Apple’s iOS 11 will offer peer-to-peer payments when it is released later this year. Snap (SNAP) does payments. (Twitter doesn’t have payments, perhaps because Twitter’s co-founder Jack Dorsey founded Square.)

None of those tech companies’ services has much caught on yet. Starting a new payments platform is akin to starting a new social media network, something that is extremely difficult because of the momentum of groups wanting to standardize. No one wants to use six payment services because different friends use different services. Consolidation keeps a standard—though this may change with different cohorts. As I was told by a 15-year-old last weekend, Facebook is for old people and Twitter is “lol.” (They Snapchat and Instagram.)

Venmo isn’t just like a social network — it has essentially become one

Venmo’s similarities with Facebook, say, extends past simply its apparent dominance of the space it competes in. Venmo actually operates with some of the characteristics of a social network, and not just because it has a public newsfeed where friends can see and “like” transactions that aren’t private.

The weirdest social network characteristic is when people send tiny payments to friends with short messages, like texts. As they pay each other back and forth, they text.

According to PayPal, a study it commissioned found that this is actually somewhat common. The study found 36% of Americans send small amounts of money to friends when they aren’t expecting them, as a way of saying hi, thank you, or to simply cheer them up. This data surprised the company, which internally dubbed it the “penny poke,” after the Facebook poke.

What a company will need to do to usurp Venmo

PayPal is very aware that Venmo’s business will be targeted by thirsty competitors looking for a piece of this growing business, especially given the potential for expansion on the international front and for commerce. But as LendEDU’s Mike Brown noted in the poll, the way a company could usurp Venmo’s dominance is by offering features that Venmo cannot.

One feature is instantaneousness of payment, something that big banks can guarantee when they work together, unlike Venmo. Venmo uses ACH transfers for most of its transactions, which uses the same tech as a check with routing and account numbers. While balances change instantly, actual transfers of cash typically take a few days. This is something that has allowed scammers on Craigslist to “pay” for something, leave, and then cancel the transaction—analogous to a bad check. (It’s against Venmo’s policy for regular people to use it for commerce.)

Banks also may have an edge with security, through Venmo has improved its once-notorious security by adding heavy encryption, multi-factor authentication, and more than doubled its customer service team to deal with problems. This, however, does not matter to users. According to the LendEDU poll, most people think that Zelle would be more secure but just don’t care. Over 78% of people said they weren’t worried about Venmo and 60% think withdrawals are “quick and fine.”

That quote is perhaps the most apt way to describe Venmo’s dominance. As Brown wrote, it’s the “if it ain’t broke” mentality that has kept Venmo on top. It’s a good lesson to entrepreneurs: It’s much easier to hold ground than to take it.

Ethan Wolff-Mann is a writer at Yahoo Finance focusing on consumer issues, tech, and personal finance. Follow him on Twitter @ewolffmann. Got a tip? Send it to tips@yahoo-inc.com.

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