To use your example of sex forums - I assume that sexforums.com is the domain your asking about
:
without the quotes there are over 5 mill results in Google - with the quotes there is only 100 thousand or so - not as much competition HOWEVER:
for with the quotes youre on the first page which is a good start
and without the quotes youre at 30th on the third page for the sex forums phrase.
With the amount of people you have linking to you that is good for Google - building more quality links and continuing to add quality content every day will get you to where you want to be in no time
Suggestion - you might look at your raw server logs and see what other terms you are coming up for in the SE's and see if you can develop some more content to place higher for those as well - start stemming out
