pt. 1
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"Yeah - the spread between markets was being brought up in IRC this morning while the rally from $10.5 to $14 was going on. "Britcoins" were being sold @ $18 a pop while $14 a pop via MtGoxUSD. It seems like it could be a great idea. I don't think the spread is generally quite so high since there was a bit of an uproar about it.
The other potential problem,ofc, is that MtGox has, by very, very far, the highest trade volume of the online markets, and aside from the PPUSD market, the rest are pretty much shit which is why they're susceptible to having big price differences compared to MtGox.