I sell a lot on craigslist and ebay and get a lot of request like this.
Most of the times they are scammers because they are too stupid to notice that they are responding to my different ads.
If they offer you extra money for what you are selling its a scammer.
As far as paypal goes, they can reverse the charge back to you within 20 days if the buyer says there is a problem.
Ebay has some protection with feedback but if you have a problem it can go both ways.
Best scenario is to have them send you ONLY a USPS money order for the exact amount, and you only ship after you have cashed it.
ritrebor