Hippy - Using DKI and adding it to your Sub ID for your network will allow you to see in your Network's Statistics/Tracking which keywords lead to clicks and ultimately conversions...
The reason I said you may want to cloak or mask your keywords is because someone brought up the point that some of the less...Noteworthy networks could look at your same Statistics and see which keywords your using and which are converting if you didnt have them cloaked.
Bubble's method of using the database works like the following (I would imagine)
The source keyword is passed into your URL and then a PHP script checks to see if the keyword is already in the database, if not, it inserts it with an auto-incrementing number, for instance - if "blue widget" was passed in the URL the PHP script would check for it in the DB and would insert it with the Id of 1, then "red widget" since it doesnt exist would insert with the Id of 2
Then, instead of passing your keyword into your Sub ID to the affiliate network, you pass the number associated to the keyword so all the Network would see is a sub id like 1, 2, 3, 4, etc.
The database wont affect your QS, its just a few lines of PHP that grab the Keyword from the URL that you already have setup and inserts it to a DB..
As far as using DKI for Longtail Keyword Phrases in your Google Ad Copy, it depends on how long they are, you have to remember that if the Dynamic Keyword is longer then the amount of chars you are allowed to use it will use the default text... So if the majority of your KWs are long and over run the char limits its somewhat pointless..