I think it's reasonable to assume that if 50k people tweeted about it, a far larger number probably took action (active tweeters are just a small subset of the population) or are at least thinking about reducing usage or deleting.
Deleting facebook has been a topic of conversation in my circle for months since I did it ~4 months ago or so. It's definitely on people's radar as far as other media seems to indicate (we've had anti-facebook threads daily for months on HN), and my friends (mostly tech people and very active facebook users) have almost all reduced their usage significantly.