Most of it started around May, but I have no idea on manufactured date for the pumps. Most of the people that have been having issues have had them die in a matter of months, or less. I've ran Walbros in everything I've ever had and never had a problem, so who knows. I haven't fully read the thread as I don't really want to know if the pump I just installed is going to give me nightmares or not.
Most of the pumps in question are 340s.
Edit: Also, a few people seem to think the problem is a grounding issue. Racetronix and other vendors recommend a ground strap from the tank to the frame. I haven't seen anything whether or not the people having failures have done this or not. Just food for thought.