that depends.
is WD claiming that their software is supported and compatible with OSx Mavericks?
or are people just using the software, and assuming that because it worked for ML, it'll work for Mavericks?
it its the 2nd, and people are assuming, than it's their own damn fault. if the product literature doesn't explicitly say "Mavericks" or "10.9" on its compatibility ilist, it is actually neither Apples nor WD's fault in the matter, but the user for not ensuring their using the appropriate software.
No. Come on.
For businesses (large enough to have IT staff) then yes, it's at least 1/2 your own fault. And even very small businesses with no IT staff should be savvy enough to realize they should not jeopardize their business by jumping on brand new versions of any software.
But consumers can't be expected to be that sophiticated. They may not even be aware they are running WD's crapware. If you sell to consumers you take on the burden of ensuring a reliable experience. And if you don't consumers will find someone who does. Put it this way: part of what you're selling is reliability and support. Unless this issue was introduced in the last M builds there's no question that WD deserves the Lion's share of the blame because otherwise they had plenty of time to test and fix their software but didn't.