Out of curiosity, what's the rationale besides setting your account up this way? If you are getting THAT granular, why not just do one keyword per ad group?
If you plan on a large amount of campaigns you should check the Adwords Learning Center...isn't there a limit on campaigns in each account?
Since you are a relatively new member of the forum, I am not aware of your level of expertise - so please pardon me if the page I have referenced below is too basic.
That said, this is one of my favorite resources on how to think about AdWords, leading to some useful insights on how set up an AdWords account for success:
Tips for success
[adwords.google.com...]
The topics covered on this page - which, in my opinion, are essential to using AdWords effectively:
1. Identify your advertising goals.
2. Organize your account for maximum effectiveness.
3. Choose relevant keywords and placements.
4. Create straightforward, targeted ads.
5. Optimize your website for conversions.
6. Track your account performance.
7. Test and modify your campaigns to get the results you want.
AWA
<edit> Correct my user name - hahah! </edit>
[edited by: AdWordsAdvisor at 3:25 pm (utc) on Mar. 17, 2009]
I've seen it done per ad group before; but never by campaign. Not sure of any reason to do it by campaign either (unless you are doing some interesting budgeting)."
My budget is less than $500. not interesting budget level. I want to set up by campaign. But can you pls tell me the procedure that how to do it per ad group. Plz explain me