Sgt_Kickaxe - 4:15 pm on Sep 12, 2011 (gmt 0)
Extensionless urls do indeed make life easier in many instances, use when possible.
I'm not so sure extension is irrelevant however. I've noticed that a .pdf document and in many cases a .kml file gets a pass straight to the top 5 as an 'alternative'. That's not very practical information for most sites since these types of documents require software a visitors computer may not have or require a download because of size.