As a result of recent vandalism, editing of this page by new or unregistered users is temporarily disabled.

http://en.wikipedia.org/wiki/Google

Strange. What kind of vandalism was that?

I guess someone attempts to add, delete or change the content of the page. The most common type of vandalism is the replacement of existing text with obscenities, page blanking, or the insertion of bad jokes or other nonsense.

You can check out what went on by looking at the History pages. Some people that werent members made various edits. Just taking one example here:

http://en.wikipedia.org/w/index.php?title=Google&diff=46160391&oldid=46075226

The article was changed to the text of Microsoft's article. You can view other changes in the history (you will see a large number of reversions – the result of vandalism) here:

http://en.wikipedia.org/w/index.php?title=Google&action=history

It looks like it all happened on yesterday. (Mar 29th)

Semiprotection by the way is not very high security. Members can remove / add the sticker at any time and members can continue to the edit the page whilst the sticker remains.