In a letter sent on Monday they note ".. NSA also has legal power to force Google to hand over the private information of its users [ie signals intelligence information.] How Google executives handle this potentially conflicted relationship is largely unknown: neither Google nor the NSA are talking."
A $26.7 million dollar renewable sole-source contract for Google Earth spatial imaging software with the secretive National Geospatial-Intelligence Agency(NGA).
A sole-source US Patent and Trademark Office contract and the use of servers outside the USA is also noted. The FBI has spent $600,000 on Google Earth Enterprise software since 2007. DHS and FCC issues are listed.
The 32 page pdf file.