Private equity firms in the buyout segment are taking more of a global view.  They are looking at buying out firms headquartered overseas.  And by necessity, this will move their business outside the US to some extent.  London of course would be an ideal location.  As an example of this, I invested in a buyout fund recently where they gave you options as to how you wanted your personal investment distributed between US and International--you could choose nothing outside the US, 10%, or 20% outside.  (should be interesting for them to administer).

Second, the reaction to regulation I've heard as it regards moving outside the US, has been focused on small companies that are evaluating going public.  SarbOx adds an estimated $2 million per year of spending to such companies, which is a big number for them.  Some companies have therefore gone public on the London Stock Exchange, or others.  The problem they have run into is there does not seem to be as much liquidity for small companies on those exchanges.  You need people buying and selling a stock actively to make a market, and I've heard that is not happening.

I have not seen much data on either of my points--information is more anecdotal.

I would be interested in articles or data on the point you make.  The regulatory issues in the US are more focused on public equity companies, so I'm not sure I understand the rationale for the argument.