I have now spent 5 minutes on the EFF site and am now qualified to hold forth at length.
More seriously, that depends on the terms of "opt-in" and "sharing" and "security", yes? Such details make nice real estate for the Devil. I'm by no means convinced that the people writing these laws understand the implications and possibilities -- I don't trust their values because I don't think they have the understanding to even have values. Or understand how those values are advanced or eroded. What opinions I have of their values are formed by the SOPA episode.
To _my_ mind, I would need to see the compelling argument for why we need legislation in the first place. At which time I'd have to go to school on this more than I have. And most of the security problems I've read about have more to do with corporations doing a terrible job configuring their own equipment than with some remarkable threat that can only be met through government-organized action.
So in general, I'm against any law without some compelling need. I don't see one here, and that might be ignorance, but that's my view at the moment.
How would I relate that to Facebook? If my view were valid, my first stab would be, "They are supporting over-broad legislation, without a stated need, that could easily go wrong. That bespeaks a centralized-solution attitude contrary to the values that have built the 'net we have today, and unlikely to found the trust needed to make the 'net work best going forward."
But even if that withstood scrutiny I'm not sure their business is going to live or die based on what is essentially a question of corporate culture. If they don't die of something else, they'll get opportunities to change their approach on this stuff.