The ones I was told no on:
Alien Encounter (although they let me tape both preshows)
Timekeeper (managed to get it all once anyway)
Tower of Terror (what's the point? The video at the beginning is okay, but the ride? Dullsville, especially on video)
Ellen's Energy Adventure (Ellen tells you; I didn't listen. I'm a baaaaad boy)
Cranium Command (yeah, I didn't listen again. Glad I ignored them)
Circle of Life (keep trying and hoping I'll get a good copy of this someday)
It's Tough to be a Bug! (yes, I did)
Honey, I Shrunk the Audience (got it from Disneyland)
Soarin' (a camcorder does well in the underseat storage bin if "stored" properly)
Sometimes Muppetvision
Sometimes Hall of Presidents
The American Adventure
There may be others, but these are the ones I recall hearing some kind of spiel beforehand about. The only time I was actually asked to stop recording, though, was in Timekeeper. Frankly, considering the way Disney keeps killing off the best attractions, I feel it necessary for everyone to tape these attractions as much as possible...and share them! Some record of their existence needs to exist, if only to satisfy Disneyphiles like myself. Now seems like a good time to visit Horizons, in fact...