A DPR Pentax forum user has been updating a list for most of the SDM failure cases that have been reported at the DPR and discovered/counted by him so far:-
http://forums.dpreview.com/forums/readflat.asp?forum=1036&thread=35746036
Here are the latest statistics, as at the time I make this post:-
"Lens - # of reported issues
16-50mm - 40
50-135mm - 34
17-70mm - 6
60-250mm - 0
55mm - 0
200mm - 2
300mm - 6
Number of lenses with issues - 88"
via https://spreadsheets.google.com/ccc?key=0AoOE9_TdlzaNdHl0U0ljXzUyR1FvX2pkRU1YZGNFbWc&hl=en#gid=0
(Good Job, Russell! Well Done! :-))
Hence, once again the SDM issue and unreliability is confirmed. But then particular fanboys would still argue and defend endlessly that the number of reported cases is small and thus "negligible" and there is far more number of SDM lenses sold so far. But I think they just lack minimal logic by saying so and in fact they have no valid argument and point of any at all.
It is because we cannot assume all Pentax SDM owners/users read the DPR forum. Secondly, we cannot assume all the DPR readers reported their failure cases. Thirdly, we cannot assume that those who have not reported did not face any problem (and vice versa anyway). But then one thing is *for sure*, for those who reported, the case is more or less the same and the reported cases are NOT "negligible", that is, there have been A LOT OF failure reports of different SDM lenses already.
If the above summary and cases for what has been reported in details at the DPR are not adequate, just go read back the last SDM Petition elsewhere online, then one can find many more of the failure report(s) (although with less details given per case):-
http://ricehigh.blogspot.com/2010/01/sdm-petition-online.html
Well, will Pentax Imaging or Pentax respond? I am afraid NOT! And I bet NOT! And I am almost for sure! It seems that they will just let the problem "go" quietly till the end of the days!! >:-| (Ned, it's your take now, will you show up? Why not discussing with the Pentax/Hoya HQs to see what can/should Pentax do?? Still busy with arranging lucky draws with the PentaxForums? ;->)