It creates potential for claims of conflict of interest... favortism.... etc. etc.
One example: Employee plays in an active guild and is known. Other guilds then begin to think (right or wrong does not matter) that that guild is getting favors or perks (like better then average drops in OPs) etc. etc.
Another Example: Employee plays in an active guild and is known. Guild members constantly needle and poke for non-public information. Even when none is shared.... some guild members will "make **** up" and claim it was told to them.. and other people know said liar is in a guild that has Bioware employees in it and much anger indignation and anguish ensues in game in and in the forum.
I could go on and on here.... but I think the above two examples makes the point.
[inb4 someone takes a shot at me once again and claims I am a Bioware employee or consultant... I'M NOT. I'm just toughtful enough to figure out why things are the way they are]
Did those examples come directly from your Bioware Employee Handbook?!