No.
300MH/s = .67BTC/day
= $5.70/day
= $171/month
And anyone with that kind of MH/s is probably using no more than 250w of electricity, so 180kwh/month, or about $18 more in electricity per month. Well, if you get decent rates on electricity, anyway. $72/month at most though.
Mining is far from being unprofitable. When difficulty hits 4M, then we'll talk about it being unprofitable for a good portion of hobbyist miners.
This is a plausible scenario. What cracks me up is the people who assume the BTC exchange rate will stay the same forever

Look at the historicals. It's only going UP.
But if you think the rate will go up, it's more efficient to buy BTC than to mine them.
I'm starting to get tired of seeing this.
If buying and selling BTC were as simple and straightforward as mining has become, it would be a good point. As things stand it's nowhere near it.
A newcomer can start mining and take his first payout in minutes. An ambitious one can build an array of machines and mine for nearly a week before his payments clear through Dwolla and MtGox.
Instant, or at least fast gratification and ease of use is very important.