“Accepting payments in cash or crypto only. Venmo not accepted,” future online sale ads might read, at least for this recent victim of fraud on the reigning “killer” P2P payment app.

Expressing his thoughts in a 32-tweet long tweetstorm, this seller of a 5k iMac (who goes by the handle @czeins on Twitter) found himself missing the $1,500 owed by the Mac’s would-be buyer, dubbed “Craigslist Jeff.”

Let’s back up for a moment: Craigslist Jeff expressed his intent to purchase the iMac from @czeins, and pay via Venmo. The transaction seemed to have gone through at the beginning, but was reverted shortly after, and flagged by the P2P payment app as a “high risk” transaction that “had the potential to generate loss in Venmo,” according to the seller’s tweets.

The seller’s account was not credited for the transaction, as Venmo is “unable to cover transactions that happen outside of Venmo’s intended use,” according to Twitter.

The seller tweeted:

“$1500 in Venmo” didn’t say “pending” next to it. It didn’t say “$1500 in Venmo if Craigslist Jeff’s money clears.” It should have. (27/32)

— Claude (@czeins) May 27, 2017

Scams of this type are becoming fairly common on the “killer” P2P payments app, leading others on Twitter to question its reliability as a payment method, especially when other online transaction routes exist—like cryptocurrencies such as bitcoin, for instance.

One of the most highly-cited benefits of bitcoin (which has made a few headlines of its own for nearly reaching a value of $3,000 per coin in recent weeks—the current price is hovering around $2,450) is its irrevocability.

Similar to a cash payment, once a user moves bitcoins to another user, there is no way to reverse or walk back the transaction—a capability of other payment methods that opens them up to the type of fraud described above.

The seller, who was eventually credited with the money owed to him by Craigslist Jeff, certainly seems to be a fan.

He tweeted:

Anyway – thank you for speaking out. Truly. (And yes, Bitcoin is totally the future, nerds.) (5/5)

— Claude (@czeins) May 31, 2017