The thing is, just like in music sales, ratings have fallen dramatically for TV in general. Expansion of internet and DVR-s, TiVos or whatever they're called,a lot of people are taping, a lot of them watching on line or just downloading torrents.
No show gets 30 or even 20 million viewers these days which was a regular number for DH in first 2 seasons. Maybe Idol can still pull 20, not sure.
Tv series now get from 10 to 15 and that's considered great. DH started this season really strong with 12 and 13 million per episode but again ABC totally screw them up with endless breaks and then returning the show against big awards shows. It managed to recover a bit by the end of the season though. It happens every year but this year was the worst, ABC put them against every big event and then when there was nothing big they put them on a break.
BTW I hate Gray's, characters are so annoying. Only watched a bit in first seasons but from I read on fan boards it really became terrible.