Maybe I am an old fuddy duddy but I don't care much for the 'motion capture' or the overuse of CGI. For one thing, often the movie becomes far too much about Hey! Look at what cool things I can do with my computer! (see George Lucas's last 3/prequels of Star Wars. ) I specifically stayed away from Beowulf, 300 and probably more because really, I don't want to see a cartoon version of actors I really like. I much prefer it when CGI (or whatever) is used where needed, to depict fantastical creatures such as those in LOTR, with the emphasis being on the very human actors.
I can see why actors would object. I can see how easily studios would gradually, oh, so gradually move towards using only CGI/motion capture or whatever in order to avoid paying actors for their screen presence. In my area, there have been some commercials which used (not sure of the technique) but it looked as though actors were filmed and then computer artists animated over the film images. I.E. like tracing way back when i was a kid. Ok technique for some things but cheating, artistically speaking and the effect was creepy, cheap and artificial. And obviously I can't remember the name of the product.