I'm not so sure. I have a Droid Eris, the same one Apple used in their video to cover up their antenna issues, and try as I might, I cannot get it to drop more than one bar. Even when I "hug" the phone, covering everything except a little strip at the top of the screen so I can see the signal, I only drop a bar.
...Other than that though, the phone's crap. But don't say it happens on every phone.
You know, I can't reproduce this on my AT&T iPhone - but that does not mean it does not happen for other people in other locations. I think it depends on many factors, including your location (and the signal strength there). I guess I could fly to NY and try to reproduce. So maybe you should grab a friend with an iPhone and you sit next to each other and try to death grip the phones (works of course only if you are also on AT&T) - and also trade the phones between you and your friend for tests since everyone might hold it different (even when following instructions for death grip).
Anyway, I hope this is not getting blown out of proportions as last time.