Here's the email that PGA communications exec Ty Votaw sent out to reporters, via Wei Under Par:

As you know, our media regulations prohibit the use of real-time, play-by-play transmission in digital outlets.  In order to enforce these regulations, beginning this year, we will revoke the on-site credentials of all journalists affiliated with outlets that post play-by-play coverage, whether those posts are originating from tournament site or otherwise.