HSBC Private Bank has become the latest financial institution to announce that it will no longer provide services to US expats. While the official announcement from HSBC Private Bank was couched in fairly diplomatic terms, it is obvious (to me at least) that this is a direct response to proposed disclosure rules and the consequential regulatory burden and potentially draconian penalties associated with doing business with HNWIs who also happen to be US expats.
In short form, the new rules which take effect on 30 June next year will not only make the banks responsible for non-disclosure by their US clients but require the banks to prove their innocence to avoid those penalties. Leaving aside the absolutely inappropriate shift in responsibility onto the banks and the very improper extrateratorial effect of the new regulations, it's worth noting that there were much easier and less costly ways of achieving the same objective (of identifying tax evasion by US persons).
Note: edited to clarify that the announcement relates to HSBC Private Bank, not HSBC as a whole
HSBC is not the only financial intermediary that will not accept US clients outside the US - it is now common to see account opening documents and investment subscription forms contain declarations that the investor is not a US person.