Ah, I forgot about that. If Facebook were to become irrelevant, it would take a long time for that to happen. By then, any phones with a dedicated Facebook button would be obsolete. Of course, that's assuming not a lot of phones aren't made with that button in the near future.
There was also another HTC phone, the Status, that head a dedicated Facebook button.
I haven't deactivated mine but I don't use Facebook anymore for events. I still get invites to parties and whatnot but I almost always hear about the important ones before it's even put on Facebook. Also, a lot of people don't even bother to accept an invites (e.g. Maybe, Going, Not going) anymore. Night clubs have spammed people to the point where they disregard events even if they plan on going. In a way, I'm glad people are going back to the plain old ways of extending an invite.
deactivated my FB account last year. dont miss it one bit. i never used it.
my favorite are the people that think FB is the only form of communication these days. "oh, you didnt know about <event>? i put it up on FB..." how about you just email it instead? if you want me to come, call me...