Doesn't say it moves the data, just that the legal entity providing service is the Irish subsidiary.
I had a client who pulled all their (encrypted) data off the Ninefold cloud (Ninefold were at the time a fully Australian owned and hosted company) when they leased data center space and opened an office in CA – due to data sovereignty concerns.
In fact Dropbox is doubly at risk, law enforcement or national security could target either (or both) Dropbox themselves - go straight to Amazon to get access at hypervisor level to their entire infrastructure.
Some people are paranoid enough to encrypt cross connects within the same facility that run between cages or floors, which is a sad state of affairs (but, in my opinion, sensible).
There is nothing to be gained by continually making judgement calls about which communications need to be secure and which don't. Like a lot of other technology, security needs to become pervasive so we can all take it for granted and worry about productive problems.
* A significant number of encryption technologies are broken or achievably breakable by the NSA
* The NSA has already or could easily acquire encryption keys from any large tech company with a court order in one of the secret courts
* The NSA has vast means for illicit access into systems and networks
I much prefer the privacy policies of more secure services, which tend to say things like "we do not have the ability to access your data under any circumstances".