Ah, yeah that’s a bit different.
It’s certainly true that if you were considered to be selling links, Google might penalise all the links on your pages. To what extent is up for debate, as indeed is the amount of paid-for links you’d have to carry before this happened. If it’s just one or two, I doubt they are going to do anything. And again, advertising banners cover most of the big sites on the net so obviously Google cannot do any kind of blanket penalty; either it needs to be able to work out which ones are paid for and just discount those, or else it will only apply the penalty in gross cases where (nearly) all of the links are paid-for.
In any case, given the secrecy offered by that the text broker site, you would assume that there is little chance of Google being able to identify a given link as paid-for, so long as it generally blends in with the site and thus can also pass a manual review.
Why do you say that? They don’t have nofollow on them.