leadegroot - 8:08 am on Jun 2, 2010 (gmt 0)
I think there is an important distinction to make in 'wasted resources'.
When I have oodles of bandwidth, I may not care how much the bots crawl, the 'resources' I am trying to control is the pages that appear in the SERPs (there, avoided the whole use of 'indexed' ;))
This would see me not 'wasting resources' by meta noindexing.
Whereas if I am on a tighter hosting budget, the resource I may be more immediately concerned with is bandwidth used. I know google can crawl 10,000 pages a day at times on some of my sites, and if I was on restricted bandwidth that would be an issue and might see me not 'wasting resources' by robots.txt blocking.
So where the resources that need to be conserved are is contextual.