In an essay published in Scientific American, Berners-Lee said that the Web is affected by elements that have 'begun to chip away at its founding principles', reports the Sydney Morning Herald.
Social networking sites that do not allow users to extract the information they put into them is a 'problem' that could mean the web is 'broken into fragmented islands', he said.
Although Facebook recently began allowing users to download profile information, including status updates and photos, it has been roundly criticised for leaving users' networks of contacts 'walled' inside its own site.
Berners-Lee warned that such a 'closed silo of content' risked leaving the web fragmented.
"The web evolved into a powerful, ubiquitous tool because it was built on egalitarian principles," he said.
"The web as we know it, however, is being threatened in different ways ... The more you enter, the more you become locked in. Your social networking site becomes a central platform - a closed silo of content, and one that does not give you full control over your information in it," he added.
Berners-Lee said there was a worry Facebook could become 'so big that it becomes a monopoly, which tends to limit innovation'.