The SR of this K-7 user is not working, but even worse, it causes blur! See the comparison photos he posts:-
http://www.pentaxforums.com/forums/pentax-dslr-discussion/73376-k-7-shake-reduction-problems.html
There was also another very similar report by another K-7 user previously. He then sent back both his K-7 body for replacement and also his Sigma lens for "updating", then he finally reported that there was no problem shortly after his brief test:-
http://www.pentaxforums.com/forums/pentax-dslr-discussion/68202-pentax-k-7-shake-reduction-problem.html
But it seems that the cause of the SR problem he encountered is not the Sigma lens, but just his first K-7 body, as he mentioned in the beginning that the same SR issue was found with his other Pentax lenses.
Possibly this user got a lemon K-7 of which the SR system just always caused blur.
But since I have never heard about similar SR issue reports for previous Pentax DSLR bodies with SR, this *new* K-7 quality issue really looks worrisome, especially when SR system causes blur instead of compensating for the hand-shake blur!(??!)
Least but not least, I think even the K-7 SR system does not malfunction, it is just not a great performer. Its effectiveness is low, especially for longer lenses, just see the results of this recent Image Stabilisation shootout test as carried out by the prestigious Japanese Impress DC Watch.