Fixing the macbook heat issue
There is a fairly simple solution, to at least reduce the risk of damaging your macbook by letting it run at high temps. I bought my 2.0GHz macbook over the weekend, it was idling around 70 - 75 C. Thats a little high in my book.
I put the macbook on the vantec lap2cool laptop cooler that I have for my AMD64 HP laptop. Within about 30 minutes of running, the macbook was running between 42 C (idle) and 60 C (being taxed). Now the vantec is pretty cool, but its a little bulky for the little macbook.
I picked up a targus cooler for about $24 at the local walmart, its keeping it idle around 48 C, and under normal conditions (text mate, iTunes, Firefox, Thunderbird) its running around 54 C. The targus cooler is pretty quiet, slim, but a little cheap. They sell some high-powered solutions on newegg.com with better CFM and higher RPMs.
Now I'm sure a lot of typical mac users are going to have a fit about using a laptop cooler that makes the macbook a little bulker, but its way better than the damage your going to do to the macbook by running it hot on a daily basis!!
Intel processors (at least recent ones) are well known for having heat related issues. AMD processors offer better price/performance with reduced energy consumption and output. My HP zv5000z which is AMD64 based, has two large fans on the base, and kicks off a fair amount of heat exhaust. That however is heat thats NOT in my system. If I use it for games, then I'd be crazy not to have it hooked up to the Vantec Lap2Cool.
Apple in my opinion are taking a bit of a gamble. They've had to trade-off heat issues, performance with keeping the system quiet. To me, kicking the fans in on the macbook is a last ditch attempt to keep the system from keeling over, hence the loud noise (high RPM fans). What Apple is likely gambling over is that most users will run the machines in a "cool place" and the average user won't tax the system. Your business, designer, etc types aren't going to be playing games on it. They are gambling that the system will hold up to the level of heat abuse until the warranty runs out, or you purchase AppleCare. Either way, I assume they don't lose money.
In terms of melting, I seriously doubt you'll see physical melting of the system. What you are more likely to see is heat related damage to electric components (either the processors themselves) or surrounding components, resulting in system failure (or odd issues like display problems, random crashes etc). Lets just say its in the best interest of the health of your system to keep it cool.
The fact that Apple has corrected this on the MacBook Pros with firmware / hardware changes, would suggest there is some teething issues with the move over to Intel, and perhaps a shift in the type of customers buying the macbook.
With the market being so competitive, do you really think Apple is going to say -- "Hey these Macbooks look nice, but they overheat, you need to get Apple Care because they'll fail sooner than expected, and you should buy a laptop cooler to extend the life of the product". This adds what $300.00 to the price of the laptop, thats already slightly higher than lightweight options from vendors such as Dell, HP etc. When you go to the Apple Store and the person working there insists that you should buy Apple Care because the system is going to fail sooner rather than later, that tells you something right there.
Now if a laptop cooler keeps the system running between 43 C and 60 C instead of 60 C and 90 C, then aside from your own comfort with the thing on your lap, keeping the system cool is a good idea. Unless you like to return things to the Apple store?