I'm a little concerned about some of the talk of 'Regulation' and bitcoin.
My experience with the FSA (in the UK) is that if you 'ask them for permission' they tend to get quite heavy handed and tell you what you should be doing, to the extent that you won't actually do anything.
You only need get involved with them if you fall 'under their umbrella', and this can be be determined by reading the Perimeter Guidance Manual -- which is only 1000 pages and available on their website.
As it stands, Bitcoin is not a regulated activity. FX itself is not a regulated activity, handling client money however is. So you could swap GBP or USD for bitcoin quite alright, just not maintain a GBP or USD balance.
Some light-touch regulation might be useful in the future. But anything remotely heavy will result in too much cost and barriers to entry, and the bitcoin commerce world will not grow out of its somewhat wild nursery status.
The beauty of bitcoin (IMHO) are what many others percieve as its weaknesses. Anonymity -- that's great, Non-reversability -- that's great. On top of this foundation, value-added services can be added that possess other features, but at a cost. The low-level, raw payment system (which bitcoin is), works well, and should stay so.