Robin Goad, our UK Research Director wrote about the surge in traffic to Facebook in the UK in response to the premier this weekend of personalized or vanity usernames. Here’s a daily chart of Facebook’s U.S. marketshare:

While we also witnessed an uptick in marketshare this weekend, up 2.8% from Friday June 12th to Saturday June 13th (personalized usernames were made available at 12:01am on Saturday), the more interesting chart trend in the U.S. is the inflection point in marketshare growth in early May.
Since May, the marketshare of visits to www.facebook.com have increased 22%. I was curious as to if this growth was the result of increased usage among the same demographic or if demographics of visitors to the site had changed. While the change in age demographics over the last month has been minimal, a year-over-year comparison tells a very striking story:

While Millennials (18-24 year-olds) have decreased by nineteen percentage points, Gen X’ers (25-34 year-olds) have increased over twelve points and (35-44 year-olds) seven points.
May’s tipping point may indicate the mainstream adoption of Facebook. If that is true, and early adopters are, in the case of social networking, the 18-24 year old crowd, where are younger Internet users flocking to today?
NB percentage drop in 18-24 corrected from “nine” to “nineteen” – Thanks for the spot Phil.