It's Paypal's fault if the company makes it appear that I have the money safely in hand... and then it turns out that I don't. If someone sends me a check, and I deposit it, within a day or two I know the money is mine and can't be yanked back.

Furthermore, they don't make it obvious that they'll do this. It's yet another "gotcha." As another commenter noted, Paypal is great, right up to the point you have a problem, at which point they're terrible to me.

No company is more indicative of the power of Metcalfe's law than this one: that another, less jerky company hasn't superseded them is amazing.

Not true. Any and all financial transactions are reversible, per US law.

They don't make it obvious that they'll do this

This is a standard policy for all electronic funds transfers, not specific to Paypal.