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.
At the rate things are going that may happen by November.
The difficulty will pass 4M:
Conservative estimate:
in late August. (30% increase for each adjustment and 10 days per round)
"Holy cow, look at that" estimate:
in one month. (75%, 8 days)