Here's one way of sorting out several Google adsense accounts;
First - why do we want several? Well, simple - by dividing your sites into chunks belonging to different Adsense accounts, smartpricing won't be such a big problem, if it happens it will affect only a portion of your sites. Also - if one account gets disabled (well, let's face it - Google hasn't got the best reputation there) it is not the end of the world. If you want to do this for a living, surely you can't put all your eggs in the only-machines-listening-at-Google basket.
Right here's how:
Put your first X sites (25-100) with one hosting provider wherever. These will all get the same IP number. Use a proxy script capable of https handling (for logging into Adsense), upload that to your host. CGIProxy is good, that is freeware and works fine (warning: you need to make sure certain technical requirements are there with your host).
When signing up for Google account no 1, go via your proxy script. That way Google will see your IP as the same as your sites. Fine, just what we want. So much for GeoTargeting. Remember to use this for all logons to this Adsense account in the future (make a bookmark!).
Then put your next Y sites with another hosting provider, with physical servers in another state. Repeat as above, create Google adsense account 2 via a proxy script from hosting account no 2. Etcetera, can be repeated as many times as you wish.
Then you need a name and an address. Different for each account.
If you are lucky enough to have several first names, say Richard Millhouse Nixon - then you can sign up as 1) Richard Nixon and 2) Millhouse Nixon. Because banks will cash cheques in both names.
When you have run out of names of your own, your wife, children etc - you need to resort to companies. Just make sure they are offshore and board is either invisible or unrelated to yourself. If you can't afford offshore (around $1500 per annum), use on-shore but then very important to have different board members.
Addresses - use your own, your mothers, fathers, your company, your friends etc. Try to spread them over as many states and countries as possible.
Sometime Google wants to have a phone no where they read you a PIN code. You can do that with free IP phone numbers that you ditch after using them once.
Remains to look at your OS, keyboard language and browser. Now it's overkill to change all these (there are programs that can simulate this for you if you are paranoid). If you stick to Windows XP, IE 6-7 and an American keyboard, you should be fine. There will be plenty of these around so fingerprint not very unique.
I'm actually running a number of sites and accounts like this and it works. Whether Google has "connected" the accounts, well we won't know until they try to shut one down - but I think it is reasonably well covered.
Use existing proxies out there - downside is that others may use them as well and site owners may not be trustworthy and snoop on your account details. But it is simpler.
Use the TOR network - downside is others using it as well for the same purpose. However it is safer against snoopers.
I'm using Tor to write this - of course. GeoTarget me and you'll get it totally wrong....
I also used a disposable email address to sign up here - they are pretty good, get them here:
Always look at your sites at hosting 1 via the proxy at hosting 1 (etcetera).