Old: Seagull Management:
"Fly in, dump on everyone, fly off". (I first head this when a company I worked for merged with another company. It accurately described the first contact with the new management, who very nicely told us his visit was 'Seagull Management' and explained what it meant.)

New: Seagull Spamming on Yahoo Groups
Two ways:
1. Spam the management, group-name-owner@yahoogroups.com or
2. Join group, post spam group-name@yahoogroups.com and leave group.

Both of these seem to be on the rise!

Now I have a new term, Seagull Spam!