Maybe this 31Three company needs to put up a blog post accusing MetaLab of "ripping off" their design. They could even put up comparative screenshots to show the obvious similarities, and could encourage their followers to contact MetaLab to register their displeasure. The directors of the company could also spend the day on Twitter publicly forwarding links to the blog post to their colleagues.
Seems like a great way to get some free publicity!
http://www.31three.com/portfolio/#campaign_monitor
http://newism.com.au/blog/post/90/building-campaign-monitor-...