Well, that's what Dana White believes apparently as he spoke in Southern California to promote UFC 104.  Check it:

"We're still pulling three million viewers every week.  I'm being totally honest with you, I believe 'The Ultimate Fighter' hasn't even reached its peak, yet. I believe there's so many people out there that don't even know that show is on even though we are going into the 11th season. As this sport continues to grow, and more and more people get into it and get involved, and one of the other things that I've always said, we haven't even hit the Hispanic market, yet, or the African-American market in this country."

Dana White has a point to a degree, but I think worded his statement poorly.  The fact of the matter is there are a ton of people that don't know about TUF, and that this is the tenth season currently airing on Spike TV.  I mean this season is a prime example.  Here you have one fighter that's heavily influencing the ratings for this season.  If you take Kimbo Slice off of TUF all together, this season bombs for sure.  I think the overall format of the show is beyond stale and the opportunity to reach it's peak has gone by more than likely.  Here's another way to look at it.  TUF 1 promoted the re-match between Chuck Liddell and Randy Couture at UFC 52.  That event reportedly did less than 300K in ppv buys although it did produce a live gate record(at the time) of over 2.5 million dollars.  The UFC events that take place domestically now have a baseline of around 400K ppv buys or so. 

Of course this year is an exception with Kimbo Slice driving the ratings so far, but if you look at all the other seasons it tells the entire story.  Here you have all these new fans coming out and purchasing the ppv events nowadays, but it's not really reflected in the TUF ratings.  You would think that if the ppv buyrates would go up, so would the ratings for TUF.  However, that hasn't really happened as prior to this season(with the exception of season 3 which featured Tito Ortiz and Ken Shamrock) the ratings haven't seen any significant increases.  Also, this season of TUF is wack and definitely not one of the best ever as Dana White has said trying to promote it.  Interestingly enough, the ratings are holding at 2.8 million viewers for the third week in a row since the Kimbo/Nelson fight.  It's rhetorical, but I'll ask anyways.  Has TUF reached its peak yet?