No, but if you're a seller without a lot of ratings, paypal will hold it in your account and not allow you to withdraw it until the buyer puts in positive feedback even if you don't ship until the money is in your account. Paypal will freeze your account (or at least that portion of it) in those circumstances.
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Bikes: 1996 Eddy Merckx Titanium EX, 1989/90 Colnago Super(issimo?) Piu(?), 1990 Concorde Aquila(hit by car while riding), others in build queue "when I get the time"