First it was the geeks...
Then came the brands... @jetblue, @comcastcares, @zappos, @hrblock, @starbucks.
Quickly followed by the B-list celebrities... @janinaz, @MCHammer, @imogenheap, @lisaloeb4real, @greggrunberg.
And now everyone from Eli Manning to Soulja Boy is tweeting. Don't believe me? Check out the recently launched "Celebwitter" -- a Twitter portal of only celebrity updates.
As was predicted many moons ago, with the celebrities come the masses; and Twitter has (no, I won't say jumped the shark) exploded over the last couple of months. Apologies for making you load so many images, but take a look at the screenshots from TwitterCounter:
Stephen Fry
Ashton Kutcher
Shaquille O'Neill
Lance Armstrong
Britney Spears
Dave Matthews
Jimmy Fallon
Coldplay
Sean Combs
With the exception of Britney and Coldplay (whose PR teams send the updates), each of those accounts is being written by the person themselves. Check their tweets with TwitPics and see for yourself.
And it's not just the celebrities who are benefiting. "Geek celebrities" have seen the same kind of off-the-charts curve in recent months.
Heather "Dooce" Armstrong
Kevin Rose
Evan Williams
Wil Wheaton
Justine "iJustine" Ezarik
One huge caveat that helps explain these skyrocketing charts: 99% of the people above (the accounts in the screenshots) are currently listed in Twitter's "Featured Users" -- a list new users see when they first join.
Sidebar: I really think Twitter should put some "normal folks" in their featured list, or perhaps let you choose a category of people in which you're interested. People who sign up and only follow celebrity accounts don't get the full value (i.e. 2-way communication) of Twitter. But that's a whole other post...
UPDATE 3/12/09: As it turns out, Dave Winer wrote that "whole other post" the very next day. "Why it's time to break out of Twitter."
I don't have recent metrics, but I think this very unofficial data speaks for itself. Twitter is indeed going mainstream, and we're about to see a sea change in behavior, etiquette, spam, and everything else that comes with a new technology being adopted by the masses.