Chances are since you're reading this the answer is yes. But are you evolving enough for your writing career? This was a question I had to ask myself, and the honest answer was no I wasn't. There was a time where you wrote your novel, submitted it and then things were pretty much out of your hands from there. Today an author is much more involved in the entire process, including promotion of the novel. So what do you need to do to keep up with the evolution of the literary world? As long as you have a computer (or access to one) you're well on your way.
Today a lot of successful authors not only have a great website, but they blog, Twitter, and have a MySpace or Facebook page. Do you have to do all of these things to have a strong web presence? Absolutely not. Like most things in life, pick the things you're good at and focus on them. If you like to chat in an almost texting style format, then Twitter might be for you. If you like to talk about all the things that interest you, post pictures, and such, then Facebook or MySpace might be for you. Blogging might be for you if you have something to share with others. The thing to remember in blogging is that if its all about you, people will lose interest (unless you're a celebrity in which case, you don't need to worry about your web presence!). They want to read about something that interests them or that helps them in some way. Once you're published and famous, then they'll love to hear all about you, but save most of that content for that point in time.
So should you wait until your published to begin all this? Not necessarily. Beginning these things now will allow people to get to know you a bit and start to build readers, which is what the publishing industry refers to as a platform. Even if you only gather a few people, at least you have begun. The best part about it is you will have started to meet people with similar interests and you'll have started to network. And as we all know, networking is key in the literary field!