Most complaints are not opposed to content farms as such in search results. My understanding of the issue is that it comes about when Google (and others) return the same data from multiple content farms (i.e., first result: farm 1 scrape of stackoverflow, second result: farm 2 scrape of stackoverflow, third result: farm 3 scrape of stackoverflow, fourth result: the original stackoverflow q &a). Prior to Google's recent algorithm changes, the first four or five results often had the exact same content, just being served from different domains with different framing content.
Again, the issue is not that content farms are incapable of answering your question. A major usability issue results when the first result happens to miss the target of your inquiry. Then selecting the next four duplicate results, also yields certain failure.
I often encountered the issue with very targeted technical searches, where a particular error message is key, and it seems that four or five sites have information that may be helpful. Good content farms manage to manipulate data in ways such that the resulting Google description is altered enough to appear distinct. Hence, I would look through three or four Google results, only getting more displeased by the repetition of unsatisfactory content.
Granted, if you don't encounter duplication, or if all of the content farms have the answer to your question, then there is no usability issue. I definitely encountered results that were not satisfactory, although I will also admit that the algorithm improvements have caused positive changes.
There was also the moral/ethical issue that rises when you see content farms displaying higher in the results than the original data provider (from which they scraped data). This doesn't effect the quality of the result, but it seems inappropriate to credit someone so prominently for automated cutting and pasting.
Privacy, as GW details, is predominantly a matter of personal opinion. If it is important to you, so be it; if not, that's fine too.