The way Paypal is run has pissed off a lot of people, and the problems almost always go back to freezing funds. A few weeks ago I read an ebay retailer who sold DVDs. One customer who had bought thousands of dollars of DVDs over the past few months charged back their credit card, the retailer's account was frozen. Not only did the seller get screwed, everyone who had placed orders was out because the money was simply inaccessable. For a business with a tight cash flow thats death.
As long as Google pays attention to Paypal's horrendous fuck ups, and avoids them, they'll do very well.