Should I Join?

Colleagues have pestered me to join LinkedIn.
I have resisted, with a sense of cynicism beyond belief.
Generally I find that when something is hyped to hysteric levels, it is a fad, and it pays me to wait until the breaking wave has crashed upon the shore to see if any survive.
I am one of those who stand back from "the bleeding edge of technology".
Last month, you guessed it, two very respected colleagues urged me to join. Coupled with a new prospecting challenge, I joined.
LinkedIn.
Not Facebook, not Twitter, not YouTube. (A nasty rumor circled the internet a month ago that those three were about to merge and become YouTwitFace.com, but I ignored that).
In the past week I've searched names that appear within my prospecting data, with no success; I've had invitations to join a Circle Of friends – I think that's its name – from two people with whom I am already doing business.
And then yesterday I received a reminder from Facebook, of all people, that three invitations from last December, January and July are outstanding.
How did Facebook get a wake-up call?
Is it too late to step back from the brink and quit LinkedIn, or is the damage done?
P.S. Another reason I don't like LinkedIn is that it pops up as a spelling error in my typo-checker; I am reluctant to add it to my dictionary because I will want to type linked in as two words from time to time, especially as I deal with hyper linked documents, training, applications and so on and can't afford to let linkedin slip through the net.