No you cant trust ebay,the whole ebay corporation is out for one thing & one thing only & that is to make as much money as possible from the sellers using the site,its the sellers who make up ebay & can be a fantastic place to shop once you learn the ropes & learn how to avoid being a victim.
If your an ebay noob you really need to spend some time there researching the sellers in the areas where your purchasing interests lie,then you need to research & learn ebay price values for what ever your interested in.
You need to learn to use the ebay email message system,if a seller posts an email address in his ad & then says do not try to contact him through the ebay email system & he will only respond to emails sent to the address he listed run for the hills,do not buy off these type ad's because the account has been hijacked,also do not ever pay a seller using western union or bank transfers,use paypal only unless the seller has boku feedback & your 100% positive he is trustworthy.
Then you need to pay attention to learning how to utilize feedback profiles of not only sellers but buyers also,just because a seller has a recent negative feedback does not mean he is a bad seller or a crook,sometimes it means he got involved with a shit head buyer who gave him a negative feedback in retaliation for the seller giving him a bad feedback,there are patterns in how people leave feedback & understanding those patterns helps the buyer be able to leap on deals that others are afraid of because of a sellers recent feedback.
When all else fails post a link here on this site & the experienced ebayers will help you determine if its a scam or not,im an ebay power seller, which only means that i pay them enough monthly fees where they allow me to use the power seller logo so take that for what its worth which isnt really anything..