Never heard of it.
Whether it would be good for business
depends a lot on who those alleged 10 million users are. For instance, if you sell industrial solvents and most of their 10 million users are high school students, it probably wouldn't be a good deal. But if they were more like a LinkedIn clone and the 10 million users tended to be B2B purchasing agents, it might be the place to be.
Can you tell from looking at the site or from reviewing other users' postings what sort of crowd is there? Does it have a lot of activity from people who seem to be the kind of folks who would be interested in what your business offers?