A lot of the reasons why clock speed hasnt ramped can be boiled down to the fact that frequency isnt the limiting factor in making things run faster. That sounds like a hypocrisy, but its not; Somewhere else is usually the bottleneck, and not at the 'processing' level due to speed. It is referred to as "Transmission Delay" (or at least that is how it was relayed to me :biggrin. This is why more cores started getting added. You can thus process more information in an equal time. For example, in perfect theory (and parallelism) it takes two cores at 2ghz to process the same amount of information as one core at 4ghz. This obviously doesnt take in to account a slew of factors that change this, but it gives a great idea.
In addition to that, there are also the physical limitations. Thermally, things get out of hand as clock speeds ramp up. Having transistors switch on and off (or going from 0v to 1v in real terms) takes time. Gate leakage in your transistors occurs. etc. Essentially we're limited by the properties of the silicon, and the laws of Physics.
The Prescott era processors were a great example of the problems with ramping clock speeds unduly, and the problems associated with it.
Good points, leakage was always and issue. You can only bulldoze so much into something in hopes of making it better but with that you ran into greater diminshing returns.
I do think Haswell will negate the bonuses I got with SB i5 2400, and prove to be a worthy successor.