One time I found a syringe w/ needle in a sewer that was wrapped up in a used condom next to a dildo, and I used it to shoot my test w/o probs...
but seriously, we all know it's best to use a new one each time, but in reality, if you can keep it in sanitary conditions and sterilize it w/ rubbing alcohol for a couple mins then you can re-use it 2 or 3 times with the chances of getting an abscess as minimal. The main thing is the point gets dull, and after a while it just really is no good to use anymore at all because although you can't really see it with the naked eye, if you magnified the needle then you could tell that the shape becomes grosely disfigured (curved and dull)... usually the stories I hear about people getting an abscess is either from unsterile gear or using a syringe/needle that has been in totally unsanitary conditions (like rolling around in the trunk of a car without the needle cover on for 3 days). I know people who have re-used their needles like 10times no probs (and yes I called them a stupid fuck to their face)... obviously, as has already been stated, if you want to be 100% safe, then don't ever re-use a needle (or gear for that matter), but the whole thing about if you re-use a needle then you will prob get an abscess is BS and the risks in general are overblown IMO.