how do you determine how much traffic an abondoned domain gets?
 

????? how

Assuming there was a site attached to that domain, Alexa ranking (which can be manipulated) and PR. Also, if the site was listed at DMOZ or Yahoo directory.

How can you manipulate the alexa ranking ? I've seen a lot of people try and fail.

http://www.linkpopularity.com

should help as far as linking goes

alexa rankings can be faked so easily...

The only way is setup a DNS scam like Verislime tried did to steal all the
expired and unregistered domain traffic

like others have said, you look at links, pr, alexa, etc to get a rough idea, but really there is no way to accurately figure out how much traffic the domain gets...

Download toolbar - navigate to site - hit refresh a few times.

it can't be THAT simple...

It helps if you have a few different IPs to do it from and a few friends - with 2 visits per day from 3 different locations over a week you should be able to get it under 100k with no problem - would take a few more friends to get it under 40k and another week :)

down is easy enuff, turn off the site :)

just delete the domain and the ranking will go down