Agreed.
Sheldon clearer here
http://www.sheldonbrown.com/dura-ace.html#10
There are certain Shimano wheels/hubs which are 10sp-only : 7800 DA and 6600 Ultegra from a few years ago, when they made them with an alu freehub body - they are the same spline arrangement, but the splines are deeper (as alu is softer) and so a 7/8/9sp cassette won't slide onto them (nor a SRAM 10sp cassette either, it has usual spline grooves).
Some other manufacturers have made these as well and they are normally called '10sp-only'.
However most hubs that will take 10sp will also take 8sp & 9sp (lower-spec Shimano with steel freehub, DA or Ultegra with steel or ti freehub, most other manufacturers too : SRAM are this fitting)
- these are usually called '8/9/10sp wheels'
Any hub that will take 8sp or 9sp will take 10sp (needs a thin cassette spacer as 10sp is narrower than 8sp & 9sp - the deeper spline grooves in a 105/Ultegra/DA Shimano 10sp cassette fit the shallower splines on the freehub no problem).
And they'll take 7sp too, with the thicker spacer detailed at the top of the thread.