I took ~4BTC from these keys. What do you mean by "useless"? Useless for you? 
You did? Please give us proof and share the knowledge of how you did it. In the process you've sucessfully cooperated on the evil plan (i.e. harming Bitcoin). Honestly, if it were a little less damaging I would have kept trying stuff. People should have stopped this when it began, yet they continued trying to get small bits of money.Anyhow, from the looks of it the number of TX is persistent but the mempool size is going down. We're currently at: 166,845 (120MB) on blocktrail. It will take a while before this goes back to normal.
He did for sure, in the past I read from him more advanced scan on the blockchain than this, he has bots that scans the blockchain for unsecure priv keys, and these things need a good knowledge of ECSDA signing and bitcoin protocol. And you can read in this thread his talk with basil, if you understand what they say. Is not that a proof? It's disturbing reading these doubts and pretending explanations. If you read this thread he gave hints, has he to do all the work for us? Without you do your homework to know and to understand?
Regarding the evil plan, I agree that the intent was this, but if Bitcoin doesn't resist a such attack why Bitcoin should survive? We can se that it resisted, and you can see that after @basil posts that amaclin swicthed his bots to clean the dust giving all profit to miners, so you should thanks them for clean the dust if you care about the mempool size problem...
P.S. If i did 0.23BTC in some hour at the right time with my "learning mess code"...