In short, not many networks are checking signatures because not many networks ar...

In short, not many networks are checking signatures because not many networks are publishing them. Take a look at this presentation from 2009.

http://www.ausnog.net/sites/default/files/ausnog-03/presenta...

I've been out of the space for almost as long, so would love to be wrong, but I think its fair to say that not much has improved on this front since then.