Dashes instead

I used to be very conscientious in my use of semicolons--I knew the rules and applied them correctly. But then I took a creative writing class, where the teacher said that he didn't like using them so much, and I started using dashes instead, first in my creative writing (which hasn't been published, btw), and then in emails and here in this blog. At this point, I'm so used to using dashes instead of semicolons, my use of them has been limited to formal writing, which I really don't do that much, since a lot of my writing is via online communication and quick notes.

So now I'm wondering if semicolons are being used less, for stylistic reasons and because people don't know how they're supposed to be used.