I do this because I want to build a solid reputation and a loyal readership of people who trust me. I’d rather make less money and still have a reader than make lots of money and never see the reader again. For me, this comes not only from my ethics but my belief that in the long term building a good profile and reputation leads to other opportunities for profit.
Don't sacrifice morals for a quick buck — At the outset, you'll want to do all sorts of things to make money online, but don't sacrifice your morals for a quick buck. Not only will you put people off, but you'll lose Google's trust. You also shouldn't concern yourself with things like Adsense or other ads on a blog before you have around 100,000 visitors per day. Yes, per day.