I must be mining at a cheaper rate than 90% of the forum users because I'm still profitable at $3/coin at these difficulty levels. I'm not sure why any of you would stop.
I get electricity @ ~$.074/KWh, so I have no problem mining and keeping profitable for a long time (until we hit about $2/BTC at current difficulty). Difficulty decrease is pretty significant, too, however. Balances it out a bit. When BTC was over $20, the profits were utterly ridiculous for miners, and I knew I had to sell as much as I could because the price increase was unjustified. Now we're at a pretty reasonable profit rate -- still high, though, considering how little time it takes to maintain miners.
@Cluster2k I think people are betting on the future much more than you're assuming. We all knew BTC mining was becoming rapidly more difficult, so people were speculating and buying in, thinking the lower cost to "produce" BTC now would make it a good investment for when difficulty ramps up later. - And I think it's clear people were speculating based on how wildly volatile BTC was at the time. However, I think it eventually came clear to people buying in the hype that the cost to produce BTC even at a difficulty 5x what we're at now wouldn't justify how much they're paying. Now we're seeing people speculate again because of the strong downward trend in mining difficulty, I think, though the downward trend in price obviously has an enormous impact, too. People are getting nervous and selling, seeing the present trends and predicting a grim future. That's how stocks work, too, and people who trade against the news after the news' effect has peaked or dipped tend to see fantastic returns. It's rare for people to trade on fundamentals anymore, and instead we see a lot of chartists with self-fulfilling prophecies speculating. Some of us still have thousands in BTC who aren't willing to see another potential 50% drop in BTC value against gov't currencies, and the present trend is suggesting that's possible, so fickle people get out while they can. I'll be holding and mining, at least until we see what happens to price after the block reward halves.
Getting the fickle miners out of BTC may be good for the value of BTC long-term, I think. When the price drops for us in BTC long, we have no problem holding until demand increases. Less supply (all else assumed same) will result in a higher price. Upward trend encourages the masses to buy more, and that's when we can sell at a higher price, sticking the losses to the followers.
tl;dr - Sell high, buy low, fuck trends, trust fundamentals, never invest more than you're willing to lose and stay out of debt.
I may need to pick up another 5970 to heat my whole apartment hehehe.....Actually that would be quite an expensive space heater! My 5970 sure does love the cold weather though, they are VERY affected by ambient temps compared to other cards. At full load they were mining at 62C (same as my 5830s and 6950s which was shocking to see) with a room temp of 58C. 
I took this picture from google images.
