Idk if it's ever been suggested, but I think it'd be nice to have a buy sell trade thread.. I've seen em done before, and they're actually quite nice... Nothing illegal of course, but pieces or anything like that ... just for an idea to show you what i'm talking about... pbnation.com has a really good one.
Doing a quick search, I found 23 threads in this forum on the subject. Here's one: http://forum.grasscity.com/general-feedback/912089-classifieds.html
As FenceWalker pointed out, it's been brought up many times and does not really seem feasible at this point. Firstly, this is an online head shop. Selling glass is how SJ makes his money. If your livelihood was running a burger stand somewhere, would you want to allow some random folks to come hang around your property selling their own burgers, possibly cutting into the business that allows you to afford your rent? Secondly, selling pipes and other marijuana related items online is a tricky thing as far as the law goes, and I can't speak for SJ, but it's not something I would want to get involved in if I were him. So unless he decides otherwise, it's a no-go for now.