I cloak just about everything in one way or another, it's an essential tool for blackhatting.
Like xu123 said, cloaking in itself won't make you more or less money. The main objectives of cloaking are a) to get more traffic through delivering more optimized pages to SE spiders; b) making more money by redirecting surfers directly to ad pages or sales pages without showing them any annoying free content.
Say you have a blog with some banners on it that gets 1000 hits per day. You might realistically get a 10% CTR to your sponsor and convert 1:500, meaning you get 100 clicks on your ads per day and then get a sale every 5 days on average.
I might cloak the same site and redirect all the traffic directly to the sponsor. Now I'm sending 1000 hits per day to the sponsor; however, it won't convert as well, because people aren't voluntarily clicking on my ads to visit the sponsor; instead, I'm just forcing them to go there. However, the ratio might realistically be 1:1000 - 1:1500. So now I'm getting a sale every 2-3 days.
That has to be balanced against the risk of getting banned.
Of course, not all cloaking is a straight out redirect; it's arguably better to just cloak parts of the page eg. delivering more text (or more optimized text) to SE spiders, more blatant ads to certain browsers depending on whether they have javascript enabled etc. Remember you can cloak js and css too, not just html files.