I was surprised to learn that 62% of Internet users are unaware of a distinction between paid and unpaid (organic) search engine results. This information is a few years old; released by the Pew Internet and American Life Project in January of 2005, one can safely conclude that the data is about four years old now. In terms of the Internet, that’s a pretty long time. I would love to know if there has been any improvement in awareness since then.
Paid placement allows the highest bidder to appear at the top of a search engine’s sponsored links. There is a question about the ethics of this practice. If there is an issue, it is really about transparency. Are the results properly identified as advertising? I made a survey of a dozen of the most popular search engines. It showed that nearly all do indeed mark their paid advertising in some way. Usually, the search engines use the words “sponsored link” or “sponsored results” or something similar. While the disclaimer isn’t particularly large or bold, it is there. Some have shaded background that help defined which links are part of the grouping. My vision isn’t all that great, but it is clear enough to me. I have included an Ask.com screen shot of a search result for “pet supplies.” I have drawn a red box around the disclaimer.

Personally, I don’t see the issue. It is pretty obvious to me. Is it possible that people don’t know the meaning of the word “sponsor?” Do they think it has one of the first four meanings?
1. One who assumes responsibility for another person or a group during a period of instruction, apprenticeship,or probation.
2. One who vouches for the suitability of a candidate for admission.
3. A legislator who proposes and urges adoption of a bill.
4. One who presents a candidate for baptism or confirmation; a godparent.
5. One that finances a project or an event carried out by another person or group, especially a business enterprise that pays for radio or television programming in return for advertising time.
The American Heritage® Dictionary of the English Language
I believe that anyone who thinks about it knows that in this context “sponsor” correlates to meaning 5. In this sense, the sponsors are paying to bring us a free search engine with powerful capabilities. Why would anyone be surprised that there is a business model attached to the equation? Here is a copy of Google’s screen shot for the same search:

I have drawn red boxes around the text for sponsored links. Again, they seem pretty clear considering the shaded background and the text that says “sponsored links.”
I find myself defending the search engines and the marketing model. So far I don’t know of any of the major ones that aren’t being reasonably straightforward in disclosing paid placement. If I were going to bring up a concern, it would be whether or not paying for placement enhances the chance that a Web site will score higher in organic rankings because the high visibility has increased the number of visitors to the site. If popularity is a factor in ranking, then that could be an outcome. That is yet another topic to ponder. Still, if we look at the examples above, we see that PetCo isn’t paying for a sponsored link, but scores at the top of both organic searches. While this is anecdotal in nature, it is proably true that a site can do well with proper optimization.