After the initial explorations with the Windows XP Start menu, we had to add a rule that fine-tuned the results: If a program is pinned, then it is removed from consideration as a frequently-used program.
For example, if you right-click Lotus Notes and select "Pin to Start menu", then it goes into the pin list and will never show up in the dynamic portion of the front page of the Start menu. This tweak was added to avoid the ugly situation where you have two icons for the same program on the front page of the Start menu, when only one would do the job.
This is another manifestation of the "Don't show me something I already know" principle, which we saw earlier when we discussed why the All Programs list doesn't use Intellimenus. After all, you pinned the program to your Start menu because you run it often. There's no point in showing it again at the top of your "frequently-used" list; you knew that already! Use that scarce real estate to show the user something that is actually of value.
Next time, another fine-tuning rule that tries to filter the noise from the results.