ADDED BONUS: many have already have all the equipment they need to get started. Like you said, it's a fun hobby.

Considering the cards overheat at above 120 C and overclocking doesn't really do anything for hashing, miners in hot climate could put the boxes in a protected area outside and suffer few ill effects.

Mine is a joke? People call it waste heat, I use and enjoy the waste heat so I made a joke about it.

I doubt a natural gas furnace even has a PCIx16 slot much less match even a budget Nvidia's hashing specs.

^See what I did there? Another joke.

Bitcoins stayed around $13 to 1 for months and you're correct, there wasn't a breakeven point for GPU mining. With Bitcoins trading at $30 the breakeven point is available again. For how long, I don't know, and I wouldn't bet a business on it.

This is the explanation I've been given for the disparity between Nvidia and AMD:
https://en.bitcoin.it/wiki/Why_a_GPU_mines_faster_than_a_CPU#Why_are_AMD_GPUs_faster_than_Nvidia_GPUs.3F

Specifically:

Secondly, another difference favoring Bitcoin mining on AMD GPUs instead of Nvidia's is that the mining algorithm is based on SHA-256, which makes heavy use of the 32-bit integer right rotate operation. This operation can be implemented as a single hardware instruction on AMD GPUs (BIT_ALIGN_INT), but requires three separate hardware instructions to be emulated on Nvidia GPUs (2 shifts + 1 add). This alone gives AMD another 1.7x performance advantage (~1900 instructions instead of ~3250 to execute the SHA-256 compression function).

For GPU programming I've enjoyed Nvidia's CUDA package greatly over wrangling OpenCL that Radeon relies on.

Waste heat? You mean my ATI Radeon 200W Space Heater® that takes away the night chills?

Haha, I'm at less than 1:1 electricity to bitcoin ratio after ~5 months.
Kill-A-Watt says I've used approx $68.23 of electricity at 11.5 cents per kWh. Bitcoins currently trade at 1 to $30 and I've got 2.2 bitcoins. The Radeon 6770 was (and still is) ~$110.

Additional factors to consider:
-The bitcoin machine is also my daily workstation so if it were running headless and otherwise unused it would have probably done better in the electricity used category.
-It makes a damn fine space heater and I've enjoyed it immensely this winter.
-My focus in this project was to learn hands-on about scientific computing applications and it's been great for that.

In conclusion: as a business it would have been a flop, partially because I haven't optimized the setup for that application. As a learning opportunity and 200 watt heater it's been phenomenal.

My AMD is cranking out Bitcoin hashes 15 times faster than an equivalently priced Nvidia so I'm okay with the results of this article.

Are slashdotters able to tell the difference between an advertisement and actual news?

So the angry hobo that stands in traffic screaming at cars will die sooner? Now if we could somehow correlate his behaviour with his genes while taking social factors into account as well.

I enjoy Asimov's stories but I had no idea that IBM was using them as a business plan.

Give a man a siphon hose and he can drive for a day. Teach him how to puncture a gas tank to collect fuel and he can drive for life.

Or something.

Good point. That sure is some nice concrete. Like to get me some of that.

But pirates commit far more crimes than the RIAA and other artist protectors.

(yes, I realize you were kidding) Hover is available for download here http://www.stanford.edu/~cammat/HOVER/index.html and here's the Weezer "Buddy Holly" video. http://www.youtube.com/watch?v=kemivUKb4f4 (Vevo account unfortunately)