These are not mining rigs. This is the sheer mass amount of people joining the network due to publicity. you would be surprised how many people took up mining when that website dealing drugs for bitcoins got known by places like gizmodo
I diss-agree with you on this one, huge amount of people cannot do this kind of compute power.
As you can see on the links i post above, there is "other" in pie graph.
I don't think these amount of compute power comes from standard people,
if "standard" people start mining, they will put their compute power into pools, so the pools graph will get bigger.
While in those graphs, the "other" pie goes huge ! So there are organization put their mining rigs to start Solo mining.