Turkey Bans Google Access for "Legal" Reasons, but Why?

Turkey has long blocked Google's YouTube service, but now it's announced an indefinite ban on Google search and other services, citing "legal reasons." Is it a sign that Turkish-U.S. relations have got sourer, or a mistake?

The statement from Turkey's Telecommunications Presidency is at once clear and mystifying. It notes that many of Google's IP addresses have been banned outright, while access to some others has been crippled so they'll take long times to load. That's pretty emphatic. But...