Google recently updated their webmaster guidelines to address the issues of linking on the web. The language chosen seems to imply that someone has appointed Google the judge and jury of morality and law on the internet.Webmaster Guidelines
Following these guidelines will help Google find, index, and rank your site. Even if you choose not to implement any of these suggestions, we strongly encourage you to pay very close attention to the "Quality Guidelines," which outline some of the illicit practices that may lead to a site being removed entirely from the Google index or otherwise penalized. If a site has been penalized, it may no longer show up in results on Google.com or on any of Google's partner sites.
According to Google here are the definition of the word illicit
# contrary to accepted morality (especially sexual morality) or convention; "an illicit association with his secretary"
# illegitimate: contrary to or forbidden by law; "an illegitimate seizure of power"; "illicit trade"; "an outlaw strike"; "unlawful measures"
While I'm sure Google would like everyone to do things the way they want I think you would have a hard time convincing any rational intelligent person that trading/buying/selling links is "illegal" or "contrary to accepted morality".
Secondly who gave Google the right to determine what was "legal" or "morally acceptable", last time I checked they were a publically traded business, not a governmental body or religious institution. Hey Google let's knock it off with the self-righteos brainwashing FUD and rhetoric, you're making yourself look foolish.