I tried to purchase Avast! Antivirus a month ago, here is what happened.
I did a google search for Avast and clicked where it said Avast2009 edition. I was taken to a site that looked like Avast home site, the billing amounts were the same as what Avast charges so I bought the pro editon with 3 years of coverage for 86.00 US dollars, I get the download screen set it up and think I’m covered. My Avast tells me that it’s gonna expire in February, I track down the charge on my account and it says, www.helpmedownload.com, the plot thickens, I go to this website and get on thier online tech chat support. I say whats the deal? they tell me that I paid to use thier website for 3 years to be able to download every useless free piece of software I want. Then they say that thier TOS says you have 7 days to cancel for refund, I didn’t know it was a scam till Avast told me it was gonna expire which was 30 days after the purchase. I told them I was gonna call the bank and tell Avast what they were doing and he instantly tells me that they are refunding my money and it will take 15-30 buisness days to do. I will now use the link that Avast says to upgrade my free version, I just thought you guys should know that your free version is being used to lure people to fake websites. ty
Hello,
Here’s some more info - http://avast.com/eng/fraudulent-sales-of-avast-products.html 
Unfortunately these wide guys are pulling this stroke with free software (not just avast) and by underhand tactics selling supposed support of their site not the free product. So they sail very close to being fraudulent.
My only advice is if you you are considering any software, be that avast or any other software, go to the home page of what you are searching for, I would thing avast.com would have been fairly close to the top of the page of results.
The problem is that Google allows the paid links to be displayed first. Click images below.
To me, Google is helping these sites to exploit those who do not know better.
Yes the Sponsored links, which you can guess I take no notice of, I prefer to view the other hits which are based on relevance, popularity, etc. So much so that in firefox I use the CustomizeGoogle add-on which can strip out these sponsored links (Remove Ads, see image).
I, too, pay no attention to those sponsored ads but noobs do not know better and therefore get hooked … thanks to Google. In my first image above, the real avast site is the first listing under the sponsored crap.
If a listing needs sponsoring, then it is less likely to be a good thing.