This is usually filled by escrow services which I'm not sure this website has implemented. Even Silk Road has implemented this, so it's a deal-breaker for me.
Silk Road has implemented this because it is a market between sellers and buyers. BitcoinStore is a company selling stuff, having escrow would have no point at all.
How does the fact that it's a company instead of an individual change the picture at all? In both cases, escrow serves the same purpose: to safeguard against getting ripped off.
Assuming bitcoinstore hasn't ripped off their previous N customers, I'm fairly confident being purchaser N+1, especially if my transaction isn't "special" in any way.
They would have a lot to lose by ripping off customers, vs. a random seller on silkroad, so I'd feel comfortable up to a few thousand dollars.
I think I've actually bought something from Memorydealers before. I'm not sure of the relationship between bitcoinstore and Memorydealers. If they're the same entity, then I'd be fine up to $100k or so -- it's a real business.
Escrow has its own risk and cost. The hilarious thing with previous online currencies (E-Gold, OSGold, Pecunix, ...) was that the escrow providers themselves were often the weak link.