Like any ebayer, I look at the sellers feedback next to their username, but sometimes this just isn't enough! It is best to always check the feedback page to see what messages were written and if possible have a look at some of their previous transactions, as sadly there seems to be a trend lately for people to 'buy' feedback by buying screen backgrounds etc at £0.01. I was going to deal with one ebayer and bid on an item that was over £100 but thankfully I checked their feedback and saw that the only feedback that they had was as a result of these penny buys. I then changed my mind and dealt with someone who had more reputable feedback, of course maybe (just maybe!) the transaction would have been ok but it wasn't a change I wanted to take... Sadly there are people on ebay who are scammers and fraudsters and so by buying feedback they may make innocent ebayers trust them, due to the number next to their username.
Buying feedback, which is virtually what they are doing is something that needs to addressed, but until that happens, avoid these people as a precautionary measure. It must be said that there may be some genuine people who would not dream of cheating anyone who have bought feedback, but let the buyer beware with these!