[netcan]

   1. The one liner  

What is your exact meaning?

I suggest forgetting about marketability, memorability, etc. of the wording, and trying to continue this conversation with a long time ebayer:

Onista is an auction-less social marketplace where people can buy and sell products."

"Huh?"

Use as many sentences as you need. Work out the meaning, then get it into a zinger. If you can't well then find another way of communicating that. Not everything fits into a one-liner. There are other ways of saying things. Start by working out what it is people need to understand before giving it a try.

  2. the terminology

Social marketplace I think that's industry jargon. Do users use the term social to describe things (social news, social networking, social bookmarking?)