Intel is trying to meet the demand for the Atom CPU found in many of the current netbooks (with some netbooks still on the horizon, including offerings from Lenovo and Dell).
The problem, according to InfoWorld, is that while Intel keeps increasing their manufacturing capacity (in some cases almost doubling it every few months since January of this year), Intel still has a finite amount that they can test at any time, and to increase the testing capacity means buying more equipment (or possibly taking away testing capacities from mainstream laptop CPUs, which they don’t exactly want to do).
Next year, Intel has a new testing and assembly facility that will be coming online that might alleviate some of the shortages, but it comes down to nobody expected the kind of demand for netbooks that occurred.
Read: InfoWorld