It has been said many times that a writer should not write based on current trends. The recent zombie/vampire craze for example. Yes, novels, movies and even TV shows dealing with these types of characters are very much in fashion and the general public gobbles them up like they are the last books on the subject that will ever be written. Of course, any writer will tell you that if you write on a subject merely for it's saleability factor, then by the time your book actually gets published the fad will be long over and all of your hard work will have been for naught.
But, should we really tell new writers that popular genres or subjects should be off limits just because it has already been done to death? It seems to me that every time I think there couldn't possibly be another zombie book that is any better than the rest, a new one comes along that puts just enough of a twist on the old clichés to make it worth while to read.
Another thing to consider is this: If these new writers take our advice to heart, what happens then? Shitty books, that's what. Trust me, I know. When I set out to write my first novel, I had a billion and one story ideas floating around in my head and yes, most of them were filled with zombies and vampires. Unfortunately for me, I read or heard somewhere that writing another zombie novel would most likely end in failure, so I threw out all of the ideas I previously had and began to write a book that had nothing to do with any of that. I struggled for months to try to come up with a plot that had not been done before. Man, was that a mistake and a HUGE waste of time. I wasn't writing what truly inspired me specifically because I didn't want my novel to be "just another zombie book."
I do agree that one should not write purely for the sake of a trend, but we must also be careful not to discourage people from writing what they like purely to move away from the trend, either. Luckily, I have a very short attention span and am notoriously bad at following good advice. So I ended up writing the story that I wanted to write and not what I thought people would or wouldn't want to read, and not only was the book better because of this realization, but I had more fun creating it, too.