There was an article about Litecoin being profitable the other day, though. (I regard Litecoin as being even more of a bubble than Bitcoin, but you could hedge by periodically selling your LTC for BTC.)
https://bitcointalk.org/index.php?topic=8405.0
Back then, when bitcoin was about $5, one guy was able to mine 0.38BTC (~$2) in 9 hours for $20 of EC2 time. Now that bitcoin is over $1000, you might think it is profitable, but mining has become more difficult than in 2011.
Bitcoin mining is designed to get more difficult over time...like listing the prime numbers, where the 1 and 2 digit ones come easy, the 3 digit ones get tougher, and so on. Intuitively, I would say that if you could put $100 into some new mining technology and get $150 out, then everyone would do it, and the low-hanging fruit would quickly dry up, and soon you'd be putting $150 in to get $100 out.