Sgt_Kickaxe - 6:20 am on Aug 2, 2012 (gmt 0)

Google captures all data they can, GWT is a way of letting us see some of what they collect and they tend to show things that we can suggest corrections for. This is likely just a way of showing us information they get anyway to allow us to see if our markup has issues or not.

It's beneficial all around, imo, but you aren't being forced to use it(until they figure out how to force G+ into it).