While I enjoy reading the presentations people post here, I've never been that happy with their using Slideshare. What's wrong with just putting a PDF somewhere? As it turns out, Slideshare is actually somewhat slimy -- they got caught using ETags to force tracking cookies on people who explicitly block them. (Do a search for "slideshare kissmetrics" and you'll see that they were proud of it.)
They're welcome to whatever business model they choose, as long as they're open and honest about it. But really, you're better off uploading your slides elsewhere.