Guest blogging?

I was reading another one of my reads this morning, 2guys2cities when I saw that the post on backup strategy was written by Mike McBride. Is that what you were *really* doing whilst you were pretending to be on holiday Mike? I've come across several blogs where people have had guests in to say something - normally whilst they are away on holiday or something. I wonder if there is a market for babysitmyblog.com :-)