Have you considered the value that registration forms are creating (or taking away) from your website?
Source: Janrain
Download this infographic as a PDF – http://info.janrain.com/acton/attachment/1205/f-00fb/0/-/-/-/-/file.pdf
Source: Janrain
Download this infographic as a PDF – http://info.janrain.com/acton/attachment/1205/f-00fb/0/-/-/-/-/file.pdf