Hi,

As Kristina said, most ppl here are regulars and 
tend to recognise each other's id etc. However 
another way is, if you do see something you like 
on someone's sale page, you can always ask if 
they have references or ebay feedback? 

Most collectors would most likely have at least 
bought something (not necessarily a cel but maybe 
an anime dvd etc) from ebay if not sold, and many 
(myself included) would have done both. So the 
feedback given would also give you some idea as 
to whether the person is reliable etc.

Hope this helps & happy collecting,
Cheers,
Winnie.