This is an aluminium freehub and you've been using a Shimano 10sp cassette ?
See Sheldon Brown :
http://www.sheldonbrown.com/dura-ace.html#10
Basically, when Shimano went 10sp, they kept the same spline
pattern on their hubs and cassettes.
But they also wanted to put some alu hubs on some DA & Ultegra wheels, for lightness.
As alu is softer than steel, they kept the same spline pattern but made the splines
deeper - and the corresponding grooves on the cassettes are deeper too.
This means that a 8sp or 9sp cassette won't fit onto these 10sp-only alu freehubs, as whilst the spline pattern is the same, the splines on the hub are too deep for the grooves on the cassettes.
Conversely, a 10sp Shimano cassette will fit on an earlier 8sp or 9sp hub, the shorter splines will go into the deeper grooves
- but it wobbles about a little.
This isn't a problem with a steel hub, but if it's alu you get wear as you can see on your hub.
Shimano have now gone to titanium hubs on their higher-end DA hubs - as light as the alu but as hard as the steel, so these have shorter splines again.
They've always stuck to steel on their cheaper hubs.
So all these will take 8sp, 9sp or 10sp cassettes fine.
Other manufacturers vary - some have steel hubs, some alu. Most usually they have the shorter splines so are 8/9/10sp-compatible.
Your Eastons are obviously 8/9/10sp Shimano compatible, with the shorter splines, but are alu and so they've chewed-up a bit.
Interestingly, SRAM cassettes are the same spline pattern as Shimano, but even their 10sp cassettes have the shallower grooves - so you can fit a 10sp SRAM cassette to a 8/9/10sp-compatible hub but not one of these Shimano 10sp-only hubs.