you could probably take it even further just by making it a lot more difficult to rank the other types of domains:

1. anything that's not a .com or .org(let's face it...if it's a .net, then it's most likely bought for seo optimization)

2. the .co.uk/.de etc, should only get a bonus in their own countries.

3. anything that's longer than 16 letters. If it is, chances are that its just a spam domain.

4. anything with a dash in the domain(the more dashes, the bigger the penalty).

5. anything with a # in the domain

this way brands would be fine, but those crappy domains that were purchased solely for SEO wouldn't be as effective. Sure, .com exact match would be fine, but that's a lot less to worry about.