I can't see a reason for another site. The only problem with this site is the timing sequence. Once you post it is fixed and subsequent posts push whatever you have to say, or offer to buy or sell, further back. I have found that an offer to sell something is effective for only a half day or so.
The auction site method of running the offer for a length of time allows buyers to see what is pending over the next hour, day or week. In some defense of ebay have we not seen problems on this board with some? I am thinking of round-robin substitutions of lesser chips for better and some people who seem to have poor mail service on a too regular basis.