Documented by whom? Is there some sort of technical documentation verifying this? Maybe a white paper?
I'm not the God of photography but I get around to to a few photography websites on occasion and take a few shots now and then. This is the first I've heard of higher pixel density sensors requiring a higher shutter speed. The only issue I've seen discussed with higher density sensors is increased noise.
Now that I've thought about it, I believe early on with the advent of digital I believe this was discussed, but those concerned with it were "pixel peeping" and not evaluating the image at the resolution and file size they actually planned on using.
I shoot the 7d HANDHELD with a 400/4 and 1.4x converter. My images are only for projection, not for publishing so I can get by without everything being tack sharp. That being said, I get a lot better results with the 7d at lower shutter speeds (as low as 1/60s occasionally) than I did with the 30d. I can also crop the resulting file to a much greater degree.
To whomever is thinking of getting the 7d, don't let this "higher pixel density means a higher shutter speed" bilge bother you.
The 7d is a fantastic camera for bird photography.
