I have bought lots of guitars on Ebay and via internet and have yet to get burned.
Some lessons:
Do your homework; decide what you generally want, what it should look like, what it should feature, what issues you are willing to tolerate. Then:
1. Demand decent photos. Most Ebay fakes can be spotted at this stage. For instance, if you see a "Gibson Les Paul" with a trussrod cover attached with three (instead of two) screws, you have a fake;
2. Know what Ebay market prices are. For used and especially vintage gear, pay close attention to completed auctions, not asking prices (as these are often grossly inflated);
Be prepared to bid or pay less than market price, but not too much less. Most sellers know what their gear is worth, and you will see very few true bargains. Do not get greedy. Someone selling a 1967 Stratocaster "for UKP 500 for a friend" is likely a scammer.
Use local pickup whenever possible.
3. Read the listings carefully and ask questions. Do not rush to snap up what looks like a bargain; and
4. Pay attention to seller feedback, especially feedback generated by seller's activities as a seller.