> If I recall history correctly, Google was the first to monetize SERPs with ads.
You don't. All major SE that predated Google did so, from AltaVista to Yahoo... I used to maintain a CGI-based wrapper for a bunch of SE (these 2 plus "USE IT!", Lycos, Infoseek, WWWW, anyone remember them?) in the mid-/late 90's that removed the annoying ads from search results.
Google was the first SE with text based ads though, from what I remember.
More to the point: where the early search engines were placing paid results directly into SERPs, Google has pretty much always distinguished its search results from advertising. Not always with crystal clarity, but reasonably well.
Early SE used graphical ads that were clearly distinguishable from search results (although yes, some search results were probably unmarked paid placements, which would be illegal in some countries nowdays).
The current situation is worse for users both on Google and competing SEs, paid text ads are put in front of and made to look like search results. On mobile browsers, you typically have to scroll past several ads to see a single real search result.
I seem to recall that results placement was being directly influenced by advertising / promotional consideration. Granted, this is ~15 year old memories, but I was generally using Alta Vista or Yahoo at the time. I could be wrong.
Google's benefits were relevance of results (you'd find what you were looking for on the first page, very nearly always as the first result), as well as speed. Not polluting results with adverts would help with relevance (advertising is often distressingly irrelevant).
