I can help you understand.

I run a meager 20 ghs hardware rig at home consisting of USB erupters, blue furies, BFL jalapeño and some  HD Radeon for ltc. Putting this together, keep it running, dealing with wife who wants to throw all my computer junk away at any opportunity is NOT for a faint of heart.

I read all this bashing of cex.io for several months and really believed that the bitcointalk collective wisdom was serving me well. Then just one day out of curiosity I looked at their website. They claimed for 0.07 btc I could buy 1 virtual ghs. That was 3x cheaper than let's say AM erupter per gh. So I decided, wth I will spend 1 btc (it was $400). So suddenly, I had almost doubled my hashrate in a blink of an eye.

I kept checking the payouts and they were fine. Then in the last few weeks Elegius where I mined with my HW at home started fail cascading. I pointed my HW at home to my GHash.IO user name. It's like any other pools, no magic - cgminer/bfgminer don't care.

Then another strange thing happened. The price of virtual GHs jumped to 0.087. I sold 1 GHs making 0.08 "profit" while still having technically speaking same 1 btc in my virtual hardware. Virtual GHs went down to 0.065 now and I bought some of it back. The major point of this exercise was that I can generate btc via mining and I have an incredible liquidity of my "mining hardware". I sold about ten Radeons via eBay in the past and believe me, it's a pain in the butt to deal with that entire scheme of buying and selling real equipment . cex.io made it VERY EASY for a small miner like me to be a part of this endeavor.

I will not pretend having any sacral knowledge of GHash.IO HW assets, but judging from my example half of the reported hash rate comes from individual users running it at homes. 

Here is the stats for my cex.io, half real and half virtual:


I hope this shed some light on why people like me are loving this new service.