Very good story and video on tifos shows up on the Wall Street Journal website.
It calls the Sounders' tifo for last season's home Portland match "probably the most ambitious tifo ever in the U.S."
For me, you can remove the "probably." Certainly the best I've seen. And really, one of the most memorable minutes moments I've ever spent in a stadium. Or even a theater, because the sheer stage-craft of the unveiling was jaw-dropping.