No security is actually fool proof some just protect better than others, though I do consider blacklist scanners one of the least affective, but everyone is used to them so they're the most used way of protection, and they do protect well enough for average users.
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SIR****TMG - Not sure I believe that part of the article since the only differences in paid/free is usually the number of updates a day it gets and/or some features that may or may not give added protection, also avira has a beta out now with a behaviour blocker that as far as I heard is supposed to go into the free version.
And its not very easy for AV's to have behaviour blockers because there's a good chance of FP's and then people will think it's too confusing and not use it.