Another thing to consider: Venmo is secure in the sense that buyers cannot stop or reverse payments, so once it's in your Venmo it's good as cash.
Except when it's not. There's a loophole that goes like this: if - and only if - the Venmo transaction was backed by a credit card and the cardholder disputes the charge with his card's issuer, that dispute takes precedence over Venmo's own T&Cs, and Venmo will reverse the payment (could be one or two months after the fact) and take the money out of your account while the dispute is being investigated. Then the card issuer may or may not find in your favor, and if they don't then you're out the money.
It can happen with Paypal too, because (a) this loophole is based on federal regulation so it applies to all payment providers, and (b) PayPal itself mentions it, however opaquely, in the T&Cs of its buyer protection program.
tt does not matter whether the disputed transaction took place under Goods and Services or Friends and Family.
It would not necessarily be fraud, it could just be a dispute over the goods sold. But the process is kind of onerous, so if you've sold something for $200 you're most likely safe.
What I know is based on experience that's two years old. Rules may or may not have changed since.