Well, I'll agree with GK on Sylvia Brown. She strikes me as a complete sham, and not even a very good one.
I know you're talking about mediums, but let me touch on psychic abilities in general. I know positively that psychic ability is absolutely real -- it's just a lot more rare than all the Madame Zeldas would like to pretend. I've had maybe half a dozen readings in my life, and two of them were on target to a degree that I feel greatly exceeded the likelihood of coincidence.
Also, my best friend is intensely
psychic. It's not something he tries
to do at all -- it just happens to him, and I've witnessed it far too many times not to believe.
As for me, I've had only a few psychic experiences, but they were big
ones, unmistakable. One of them was a premonition that I believe ended up saving the lives of my parents.
So the phenomenon
is real -- but many of its supposed practitioners are fake.
You mention that this medium talks about your dead loved ones, and that makes me think of John Edward (not John Edwards, the presidential candidate -- just Edward, no S). Years ago, I watched his TV show for several months, and I came to the conclusion that it's easier to believe that he really is speaking with ghosts than that he has managed to pull off such a huge and convincing hoax involving so many people.
I attended one of John Edward's seminars a few years ago, and I came away further convinced that he really is a medium. I didn't get read myself, and I think I know why: because my reason for being there was minor, while all around me were people in profound pain. I talked to two women whose children had been murdered, a man who had been at the wheel in an accident that killed his wife... people who really, really needed the peace of mind that a reading could provide. And many of them got it.
The TV show would be hard enough to fake -- but if the live seminars were part of a conspiracy, it would have to be a fantastically complex one. Because John Edward is not telling people standard stuff like "There's an older woman who says she loves you and she's all right." He's telling people about the odd off-brand of pudding they used to make for Uncle Sol, and the way Mom always kept her cash pinned inside her lingerie, very specific things that clearly identify specific people and their unique relationships to each other.
By this point in his career, he would have to have conspired with thousands
of people around the world to fake these things. He would have to work out scripts in advance, different every time,
with 30 or 40 people per seminar... and somehow keep all those people from ever
revealing his deception. I find it much easier
to believe that the guy really is talking to the dead!
So... I say yes, mediumship is a real phenomenon. It can
be faked, though, so you should approach it with healthy skepticism and see if you become convinced. Good luck!