Here we go again: AT&T files patent infringement suit against Vonage

On Friday, AT&T filed a patent infringement lawsuit against Vonage.

The filing, in the U.S. District Court for the Western District of Wisconsin, alleges that Vonage infringed on an AT&T patent relating to telephone systems that allow VoIP calls to be made using standard telephone equipment.

Don't yet know enough about this action to comment conclusively, but here are a couple of initial thoughts:

Why is AT&T suing right after Vonage settled infringement claims with SprintNextel for $80 million? Could it be that AT&T perceives that Vonage is in a "let get this all off the table" mood, and the time to exact a pound of flesh against a competitor - one who is also fighting them in the net neutrality arena- is now?

Less consequential, but more head-scratching: why the filing in Western Wisconsin? Is this an attempt on AT&T's part to seek a decision in a U.S. Court their lawyers perceive to be friendly toward patent holders?

Hey, lawyers "shop" for favorable judges. No surprise then that they shop for favorable courts, court districts, and juries.

Anyhow, investors hate uncertainty. Look for Vonage stock- already sliding back down after the initial euphoria that followed the settlement with Sprint earlier this month- to significantly dip on Monday. After hours on Friday, Vonagestock ended at $1.28 a share, down 26 cents from the closing price of $1.54.