PayPal makes no guarantee at all for even a penny of the money deposited on an account, and reserves the right to freeze the account for any reason, at their own discretion. If that does happen (and you have no control over whether it might because a transaction from anyone f.ex via a stolen credit card to your account suffices to taint you regardless of your track record), then you are at their mercy to decide whether or not they will give you your money, without granting you any rights to be informed of the grounds on which the decision was taken. (Note that frozen accounts can still receive money their owner won't be able to withdraw.)

If you want more information about the whole ugly mess, try http://www.paypalsucks.com and http://www.paypalwarning.com.

Makeshifts last the longest.