1. Does AdSense clutter it up?
2. Does anybody make any money from this?
3. How much traffic do you have to have to get any measurable return?
1) AdSense may clutter your blog and maybe not. It depends as one person wrote how you place the Ads on your blog. You get to choose if AdSense will clutter your blog or not.
2)Yes, I make money from Adsense. You have to make at least $100 before Google will send you money. It took about three months before I got my first check from Google. Now I'm blogging to the bank and making money consulting others how to do the same.
3)You need targeted traffic to your blog. Of course, you want increased numbers, but it has been my experience that you most want your target audience to visit your blog. For instance, I have a blog on self-publishing your own book, several on the music business and one on the modeling industry. All three blogs are targeted toward their respective audience yielding me a higher click through rate even though I don't have 15,000+ unique visitors a month visiting my blogs.
My goal is to help people while helping myself. For me it only makes sense that my blogs and websites would have the potential to generate residual/passive income given I create content that is useful for my readers.
If your blog is of great information there's no reason why you shouldn't have the ability to be financially rewarded for your efforts. In addition, your blog may be turned into a paperback book or ebook yielding you another revenue stream.