Man, when dealing with Ebay it is almost a hit and miss thing.
ALLWAYS check feedback. If you think there may be a problem Do not bid. As a seller on Ebay the individual has sworn to understand and follow the TOS agrement put forth by PayPal and Ebay, so unless they erally screw you you are almost allways covered. The only thing I could think of in a (worst case) scenario is a person selling a high dollar item and then shutting down all his accouts and running for the hills or something- But I am pretty sure Ebay guards against things like that. There are people on Ebay who make a living out of scamming others, for instance some people sell an email list of sites where you get "free" goods, like an Ipod. you get the email and it is a list of popups you get everyday on your computer. Notice thier feedback. they dscribed everything perfectly in the add, and others don't want negative feedback as well, so they put something like "got what I expected..." or the likes. Ebay is a VERY touchy place IMO and I too have been ripped off s a few times, but I grin and bear it.
Chances are, if they put everything in big bold letters and have thier own little header and buyer specifications they are a reputable dealer. BUT, if someone put in huge letters, "TRUST US! WE HAVE PERFECT FEEDBACK" I would about-face and high tail it like Nitro_Freak1 was selling another model.
In any case, write them. Find out where they are and if they are for real. If you need to get a phone number and verify.
Buying ANYTHING on the internet is ALWAYS risky, but some choose to take that risk and most of the time they are rewarded with a good buying experence. Just be carefull man.