I searched the forums for 30 minutes before replying to this on-topic and very current post, so please quit replying "search before posting" to every post you think you know the answer to.
It's rude to say the least.
I even looked for info from the "guides" section of MR, and found the page you linked to, and found the information there lacking, not to mention contradictory to what has already been posted in this thread. It doesn't address all of the issues, and doesn't address c2d macbooks at all, only cd macbooks and c2d MBPs and santa-rosa MBPs. Hardly definitive.
I've read so far that:
1. you can only use .5, 1, or 2 gb chips in a C2D Macbook.
2. You can use only 2x1 gb for a total of 2gb
3. You can use 1x2gb + 1x1gb for a total of 3gb without dual channel speed bump
4. You can use 2x2gb but only 3gb will be readable, but you will have dual channel speed
5. (somehow my list skipped #5, so here it is

macbooks are cool
6. If you put 2x2gb into a macbook, it will blackscreen, no dice, no way, no how
7. You can use 2x2gb and 3.33 gb will be usable, ~700 will just disappear
8. You can use 2x2gb, and 3.33 will be addressable, but the extra ~700 will be used for the onboard graphics' chunk of the RAM (since it's shared), so you will actually, truly HAVE 3.33 gb of usable RAM, no RAM tied up for the graphics system.
9. You can use 2x2gb, and all 4 gb will read.
Clear as mud. Because I searched the forums. OWC offers 1+2gb for the macbook, but not 2x2gb kits. That leads me to question whether or not you can even do the dual channel 3.33 gb setup as claimed in this thread and others. Someone mentioned a post where someone got 4gb of usable RAM and had a screenshot. I didn't find that while searching for all sorts of things:
macbook ram limits
macbook 4 gb
macbook 3+ gb
macbook c2d ram
macbook addressable ram
more than 2 gb macbook
this place isn't exactly wikipedia.