I apologise in advance if this has already been covered.
I haven't seen it for myself. I went at the start of the year and wanted to head back during my holidays so I spoke to some people and someone mentioned:
Seven of the clubs/bars along the river have been shut down (in July 2012 maybe) and any slides or ziplines or the like no longer exist in the governments efforts to clean up the area. Apparently the bars and stuff that are left are those that could afford to pay off officials, so they are the better ones anyways.
EDIT: Its already been covered in this post http://www.travelfish.org/board/post/laos/19491_big-changes-in-vang-vieng-
So I read up on it, to check if it was true or not and turns out it is.
Also discussed here on Thorn Tree: