Si... Martin mi stupisce sempre... 
Dave Glover has held onto the title of world's smallest Team Foundation Server instance since August 2006. However, I have a confession to make. ...CUT...
Courtesy of the good folks at SizeEasy.com here is a comparison between my Mac Mini, Dave Glovers Mini ITX system in a Morex 3888 case and a can of pop.
...CUT...I'm not sure if virtualized instances count in the World's Smallest TFS Server book of records, but maybe now you can see why I was surprised when it worked so well :-)