As Facebook is growing, first becoming the largest social network in the world and finally surpassing MySpace in the US in May, it looks like the age of its users is growing with it. A new Hitwise report shows that the average age of the Facebook user has gone up with those between 25 and 44 years old, now making up more than half of the social network's user base, growing from just 32 percent a year ago.

This continues the trend of older users signing up for the service, as the rise has been apparent since March, when the numbers of users over 35 doubled over the previous two months and when the majority of Facebook users were already over 25. In one year, from May 2008, the 18-24 year old segment decreased as a percentage of the whole Facebook demographic from 38.55 percent of the visits to just 19.40 percent. This while those between 24-34 years old grew 12 percent to 27.34 percent of the visits, and those between 35-44 years old grew from 17.20 percent to 24.78.

The stats also show an increase in the overall US Internet market share this weekend, coinciding with the release of Facebook's Vanity URLs, which have spurred many users to visit the site to claim their desired username. Overall market share grew steadily in May, from below three percent at the beginning of the month, to a little over 3.4 percent on June 1.

“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,” the report specifies.