If you type terms like 'firefox' into google search much of the time the top result (which is actually an ad) takes you to a site offering a version of firefox bundled with toolbars and god knows what other malware. The story is similar for other popular windows downloads. I've even seen these ads crop up for things like Chrome in the past.
For example, here is a search I did just now for the term 'download firefox'. The top result is an ad leading to malware: http://i.imgur.com/Ote9c2k.png
Imagine having to explain to an inexperienced computer user how find to firefox or other common software, without clicking on any of these landmines google carefully disguises right at the top of the results.
I've been bringing this up on HN for a while now and nothing has changed. Many of the sites are the same as they were a year ago. Google does manual review of adwords sites. The domains of these sites have been the same for at least a year. Google knows exactly what is going on, making them just as bad as donwload.com in my view.
Google search ads are probably one of the biggest vectors for malware these days, along side the kinds of big download button ads you see on software sites (many of which are also google ads).
As an aside, I wonder how prevalent the adware would be when searching for "download chrome"?
µBlock is especially good for this as some of the lists have additional rules specifically targeting malware sources, and it can block things like actual script tags and such instead of just hosts.
Well it's not there to sell cars so much as it is to say to the public "BMW are valid cars"
So just having the advertisement get seen is what's important to them. At least that's my understanding. Evaluate the argument for yourself: http://www.reddit.com/r/explainlikeimfive/comments/14y695/el...
It's also another reason I filter ad's. I'm afraid they will manipulate the way I think.
 See http://blog.opendns.com/2007/05/22/google-turns-the-page/