You also have to factor in hardware depreciation costs.. New video cards come out all the time, usually once a year but can be sooner... and also the fact that other technology could come out and disrupt your entire "large scale" operation (ASICs etc). Technology moves very fast - it's going to have to be higher than $.30 per gigahash. At that rate you'll almost certainly go negative, unless you play the markets and make sure to sell your hardware at the right time.
I think only means it will get more difficult to even enter the mining business without the capital to put into the hardware. Which is really no different from any other type of competitive business. Only the businesses which invest in efficiency survive.
More likely, if it reaches $0.30 per day per ghash, it will be more like F@H. Only enthusiasts will support the network. The rest will just buy. Of course, this means less security on the network overall.
Some of the best efficiency ratios I've seen is around 2.2Mhash/Dollar. That's still around $500 per ghash. 1 Ghash would be $108 per year. You're still negative by $392, after a year.
So you'd have to sell the hardware for more than $400 to make a profit after 1 year of use. Not likely in the tech world.