Ask HN: Are paid text links and sponsored posts a valid business?

I'm an indie hacker and love to build stuff people want. My sites get half a million pageviews a month. Wich makes me only about $500 via Adsense. I often get requests from companies that want to pay for a text link or for a guest post. So far I never replied to them because it seems to be a shady business. On the other hand, letting advertisers spy on my users is shady too. What do you guys think?