If you happened to attend the Australian security conference, AusCERT, last week and picked up a free USB key at the IBM booth - don't stick it into your computer. Ironically, at an event devoted to fighting the malicious software epidemic, IBM's "gift" was infected with a virus.
Accidents do happen, but you might think that companies planning to give away free wares at exhibits of this time would maybe double-check to ensure that they don't end up with egg on their faces. Meanwhile, we advise that you pass on any such free gifts in the future. This isn't the first time it's happened, and probably won't be the last.