Over at Slate, June Thomas recently wrote about the way that a lot of the newer procedurals use gimmicks that mean the audience can't really play along with the mystery. (Alyssa Rosenberg responded here.) I corresponded with June about this a bit as she was working on the piece, and then figured I might as well share my view on things. An edited version of my emails to her is below.
I don't think any of the American procedurals I watch are up to the traditional fair play standards of mysteries, so these new examples seem like a greater degree of an existing issue rather than a new thing. The Mentalist and Psych both have the super-observant fake psychics pulling things out of thin air, Bones has surprise scientific breakthroughs that the viewer couldn't possibly predict, etc. I'm not sure it's possible to give a sufficient number of clues in the one-hour television format. I do prefer when they try, of course. (For background, I've been a big fan of mystery novels since way before I started watching TV, and it DOES drive me crazy when they don't give the reader enough clues.)
Unforgettable IS particularly egregious about this, as you say, but I think the mysteries don't have a lot to do with why I like it. It hits a few emotional notes for me, including the memory thing - my memory is nothing like hers, but is abnormally good enough that I've run into similar interpersonal issues because of it. More generally, though, I think I like these shows because I like watching smart people work together to make the world a little bit of a better place. I care more about solid character development than about the particulars of the mysteries themselves.
There are some shows - The Good Wife, The Vampire Diaries - that I watch very closely and spend a lot of time thinking and writing and talking about, but I like having a few procedurals as brain candy for when I'm multitasking or just tired. I use The Mentalist and Body of Proof and now Unforgettable for this purpose - characters I like but am not overly invested in doing vaguely interesting things and being clever for an hour. So it's more about which characters I want to spend time with than the actual mysteries. (My impression is that I use procedurals the way a lot of people use sitcoms - I've just always been less of a comedy fan.)
So, to sum up: I agree that Unforgettable is cheating, and would rather it didn't, but so far I like the show in spite of that because trying to solve the mystery isn't the main thing I get out of watching it.