I suspect a lot of what PayPal does (e.g. freezing accounts with "suspicious" transactions and refusing to unfreeze until you provide proof you are who you claim to be and proof of where the money came from/where its going to) has to do with the international rules designed to prevent money laundering.
Additionally, an unscrupulous person could take advantage of the current uproar over Internet privacy by claiming that they would develop a snoop-proof email system, collecting those plentiful community-funded dollars, and running off with it. Wish I'd thought of it myself, actually. The guys at paypal pretty clearly did