The type of sellers to avoid on eBay - in regards to buying drum gear...
People who describe the drums as "wooden" or "metal", in the details. For example; "Really nice wooden Ludwig snare drum...with sparkley blue finish".
Anyone who spells "bass" drum as "base" drum.
Anyone who is selling "symbols".
The casual guy who says something like; "They look like they're in pretty good shape but I'm not sure, I'm selling them for a friend..."
Folks who list drums or cymbals as "NEW!" when you can clearly see the heads of the drums are played in, stick marks all over cymbals, excessive fingerprints & dirty surfaces, etc.
Anyone who has clearly measured the drums with the hoops on, i.e. "sizes are 17.5"x18, 13.5"x11.5, and 23.5x16".
...this was spontaneous after window-shopping on eBay, I'm sure I'll think of more later - add 'em if ya got 'em!