If you're trying to market your product, there is nothing as powerful and successful as email. Yeah, your crappy newsletter will probably just get deleted by 95% of people who get it, but the cost/benefit is still in your favor.

If you want to be a success in business, sometimes you have to take off your "indignant customer" hat and put on your "trying to make a sale" hat. Don't be a jerk to your customers, and make it easy for them to unsubscribe, but setting up a periodic newsletter is an amazingly awesome way to get repeat business. Don't not do it just because you think your product or service isn't a perfect fit. Let your customers be the judge of that.