Upload & Sell: Off
Two things to consider:
1. How good is it at stopping bad guys
2. What's it cost, both in $ and system/operator load.
Several good sites do the effectiveness testing for you. This is one of the best:
Unfortunately, they report that all anit-virus programs are less than perfect. Scoring 95% is considered good. Would you fly on an airline that crashed 5% of the time? Probably not, but you have to fly.
The best freebies, like MSE, Avast, and AVG, compete well with the $$ boys. Basically, you get 90% of the effectiveness performance for 10% of the cost (no dollars, but some of your time and computer resource).
Then I discovered the free "No Script" add-on for the FireFox browser. Been using that combo for 3 years now and have had zero infections. I use MSE as backup, but MSE has not trapped anything during that time, simply because it didn't have to.
Firefox No Script does not protect against malware in downloaded programs, or e-mail attachments. So a good scanner is still needed for those. MSE is OK, so are the other freebies. I also use MalwareBytes' free stand-alone scanner whenever I download some off-brand utility.
With Firefox No Script, you can display a list of "blocked" scripts. That list is often very scarry. Even on well established "reputable" sites, the list will show a large number of blocked scripts from other sites. You might trust the "reputable" site, but do you trust all the others? Does the reputable site regularly police the other sites it uses? Even if those other sites are also reputable, are they immune from hackers that might replace their normal scripts with something nasty?