Its quite simple, if you are a "crook", will you really bother posting 25 times in order to get the chance to do bad business ?
On the other hand, if you see someone with 300 or even 1000 posts here. That person has a reputation and its likely that a) they don't want to lose it, b) Others have a pretty good idea of how that person is.
What that means is that I am more likely to trust someone well established here. Say Supaflyx (2000+ posts, helpful with others), well I am more likely to trust him than someone with 1 post who registered with the sole purpose to sell something. It does not mean that person (or Supaflyx for that matter) is or is not a crook, but just the fact that member contributed helps with trust. Its not a perfect way to do, but it is meant as a protection for every members here. I know that personally, when doing trades here, I will look at the broken ratings, the number of posts (and the posts themselves if I am worried) and the join date to get an idea of who I am trading with.
If there were no such requirements, what would make HWC different than craigslist, aside from the fact you have a name here.
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