It's worse than that.  Without miners, no transactions are confirmed.  Miners make the network work.

I started on cex.io less than 36 hours ago.  Only deposited .25 BTC, which bought me 3 GH at the time.

With some BTC and NMC mining income and some casual trading, I now have 3.5 GH.  More than a block erupter's worth of additional hashing for doing very little.  At the current trading prices, if I cash out right now I'll end up with .30 BTC for a 20% gain in less than 36 hours.

As I understand the maintenance fees, it currently ends up being 2.4% of mining income.  I've seen pools charge more than that.

I'm not paying for electricity.  I'm not waiting for hardware to ship.  I'm not dedicating additional hardware to run mining.

And no, I don't have any referrals.  Nor do I have a referral link in my .sig.