Smart CPU mining can still be profitable.

I've got ~75 single CPUs doing about ~16KH on Cryptonight... each one cost me $20-35 bucks (Xeon X5660/X5670). So average $27.50 each = $2062.50 cost for around $700 a month even at todays low profit (they have more than paid for themselves during the peak times in my case).

Also quite a few used quad-CPU servers crunching away...

Now... buying NEW CPUs with the express purpose of mining is NOT a good idea... but used gear can do nicely.