Well this is exactly the reason GM does not want to introduce their own exchange. Cause everyone would sell, dump the price down and leave.
This has already been addressed before:
3'') The question of why we are not offering hashpower trading is very good and we had long discussions about this already more than a year ago. The reason why we are not doing this is because we would need a licence for securities trading from the SEC. Most of the competitors who offered this service already received subpoenas and are not operating anymore. We have a lot of responsibilities towards our customers and doing anything that threatens our operation to that extent is not acceptable for us.
...
All the best and happy mining!
Marco Streng
According to FinCEN ruling cloud mining companies that simply pay out mined coins to the customer are not labeled money transmitters, see http://www.fincen.gov/news_room/rp/rulings/pdf/FIN-2014-R007.pdf Others that offer markets and exchanges (where the company transfers coins on behalf of customers to other customers) can be labeled as money transmitters.
And this following article is interesting as it tells us that getting proper licenses is (too) costly, and therefor you can assume failing to defend your business in US court as not being a money transmitter is even more costly/deadly: http://www.coindesk.com/bitcoin-law-money-transmission-compliance-avoidance
So... What is safer? Investing using a company that's making sure it's still operational next year and beyond, or investing using a company that may not have the required licensing to service US customers or to operate inside the US?