If MtGox does go under it is going to pummel bitcoin value - and as a consequence possibly result in the ASIC revolution stopping dead as orders get pulled and manufacturers go under.  After all who is going to buy a USD 5K mining rig when BTC is worth <$10.

As to the idea that brokerages that make 0.6% on each transaction cannot go bust - just google John Corzine. Remember MF Global......

this needs a sticky

The problem with restricting newbies is that it is offputting to the casual investigator who may be looking at starting to use bitcoin or other crypto currency. The major purpose of this site and the community in general should be to expand the number of people using bitcoin - and promote its acceptance and the understanding of it. Creating artificial impediments for new users and or otherwise putting them off by being rude/obnoxious or generally boorish is detrimental to the adoption of bitcoin by the broader community and hence its value and its future.