First off I don't think having "this week", "this month" or "this year" is a good idea; while it's computationally cheaper than the equivalent "last 7 days", "last 30 days", "last 365 days" it becomes kind of useless every Sunday (1st of month (like, uh, today), 1st of year).
This really becomes evident when you see a user's top tags and realize they all come from the same recent question. (Paul Nathan's top tags, e.g., are careers, feature-request and status-planned; hmm, why is that familiar...)
That "problem" (I don't think it's a feature anyway) is also caused because IMHO week reputation and weekly top tags really are kind of meh; it's just not enough data to be representative. The user page would go from "always the same faces" to something quite more transient (and random); I'm not sure I like that.
The situation is even worse on new, low activity Stack Exchanges. Let's look at Bycicles:
Yup! I just signed up. Our favourite unicorn shepherd also gets some first page action with his 1 rep change (or rather, -1 rep change).
Association bonus and downvotes counting in the leagues have been fixed in the meantime, as Jeff points out.
Here's what that users page looks like with two months of data.
So yes, I'd rather see a last rolling quarter window for something both more dynamic than what we had, more stable than what we're having and more interesting overall.
(today-7) ~ today(: