We're not going to shut them down by invalidating them one at a time. You're not plugging a few leaks in a dike; you're trying to splash the ocean back with teacups.
I'm not doing anything close to as good a job as a patent examiner would do, but with about an hour of work I (hopefully) was able to start pointing to some prior art that could get an examiner quickly up to speed on what the state of the art is.
I agree the amount of work involved to comprehensively invalidate a patent would be days - hopefully a group can do the same with shorter time contributions.
Unless the rules are different for this process, every piece of prior art that you point to now that an examiner doesn't agree with / understand is a piece of prior art that can't be reused further down the line (e.g. in a trial).
In 2011 there were about 500K utility patent applications: http://www.uspto.gov/web/offices/ac/ido/oeip/taf/us_stat.htm Many of those are not software related.
There are about 1.3M programmers in the US alone: http://programmers.stackexchange.com/questions/19720/where-c...
So 20 teacups each to have each patent looked over 10 times? Sounds doable to me.