There could be many reasons why you would want to do this, most common - you get more and more good e-mails into spam folder.
Ironically, today in my Gmail spam folder I found message from Gmail itself called "Welcome to the new Gmail inbox"...
In short - you cannot disable Gmail spam filter, but you can create your own filter which will override Gmail spam filter in some way:
- go to menu Settings >> Filters >> Create a new filter
- in the field "Has the words" put this: from:(@)
- click on "Create filter with this search »"
- tick the "Never send it to Spam" option
- click "Create the filter"
This should work.
