A Warning : My Paypal account has been hacked and £615 removed using it. I tell you this story so you can be aware of a clever attack vector and hopefully notice it if it happens to you - it isn't obvious but it is bloody clever - I have managed to get the money back and am ongoing in conversation with PayPal. This is how they did it :
Somehow my Paypal account username/password became known to the perps. Once they had access to it they began Spam bombing me over a period of 2 days and approximately 6000 emails later my gmail account didn't know what was and wasn't spam - as a result of this the email advising me of the transaction actually ended up in my spam filter (together with the 6000 emails) which made it almost impossible to spot. Fortunately PayPal flagged it as 'suspicious' after the spam bomb had stopped otherwise I may not have noticed it.
I suspect (although I can't be certain) that my password may have become known because I used the same one with Evernote which was recently compromised (although Evernote say that passwords were not captured by the hackers they insisted that all users change them... ahem)
The short message is - if you suddenly start receiving a lot of spam don't ignore it. Fine tooth comb your email (both legit and spam marked) as it may be a cover so that you can't see the notifications. Also change passwords on all money related sites and email accounts if you think anything is suspicious