Me.dium co-founder David Mandell on "social browsing"

Founded in 2006 and launched last August, Me.dium is making a bet that people will not just want to meet other people online, but will want to surf together to the same Web sites - a relatively new concept known as social browsing.

The company has built a browser plug-in that lets users see what others are doing on the Web, and lets those other people see what they're doing. The technology is a "real-time map of the Internet based on the activity of actual users," says David Mandell, Me.dium's co-founder and VP of marketing.

That detailed knowledge of Internet users' habits would be of great interest to advertisers, but it's also likely to raise privacy concerns, and may create some friction in consumers adopting the technology.

It requires users of the tool bar to be OK with others knowing what sites they've been to and when. That was the type of information that led many Facebook users to opt out of its Beacon program and that led many privacy advocates to express concerns about it.

Mandell says that because Me.dium users have to download the tool bar, everyone who uses it will know that their surfing habits are being tracked, and that hasn't stopped users from using it to track down where their friends are surfing to online.