We don't generally discuss ethics here. We discuss link building strategies. There are guidelines the search engines would like webmasters to follow, but that has nothing to do with ethics.
Are you asking if the above scenario follows search engine guidelines?
If that's all you have that's shady, you're probably not going to raise flags. I can think of a number of scenarios why doing that makes sense.
Would it pass a hand check... in my opinion it probably may raise an eyebrow, especially within certain contexts.
