All of these sites are free to use and require you to register with them. Once you have registered you can begin sharing links.
You will not need an account with CLIP to do this. When you click on a site's logo a pop-up window will appear. CLIP will not ask you for any personal information during this process.
Why Facebook, Twitter and Google+1 buttons?
We are reflecting the preferences of users in the UK. Currently Facebook is the largest social network and Twitter, although having a smaller audience than Facebook, is growing faster than any other social site. Both also offer the technical capability to enable sharing activities. The new Google+1 button enables you to recommend content on Google search.