It's a double edged sword really. For the fighters, I guess it makes sense that they'd want to fight as often as possible, taking on the best of the competition outside the UFC across all organisations and to get the chance to sell their name to different audiences. However, for the actual organisations it doesn't make a lot of sense. Take DREAM for example. Their big cash cow and poster boy is Shinya Aoki. They sign a deal to send him over to Strikeforce, hoping he'd come back to Japan with the SF LW title and secure a big 1-up on American MMA. That didn't happen though; Aoki was outclassed, and now DREAM and Japanese MMA look inferior to Strikeforce and American MMA. How did that possibly help DREAM in any way?
Why would any company be happy for their fighters to put any marketing work they've put into them in jeopardy by travelling around the world fighting guys from other organisations? Sure, if they win then it looks great, but if you've been hyping up a title contender and then he goes across to Japan and gets whooped, it's going to be hard to convince fans to get behind that hype again. There's also the issue of potential injuries, which could damage any plans 1 company could have been having for a certain fighter. It makes perfect business sense for the UFC to sign their fighters to exclusive contracts, and the only reason Strikeforce don't do it isn't because they're super ethical and are working for the fighters, it's because if they brought exclusive contracts in, then guys would just leave for the big show. Opening their fighters up for fights in Japan is a USP which could tempt guys in; the non-exclusivity and willingness to co-promote certainly helped them secure Fedor's signature for example. However, if Strikeforce are going to be around for the long-term, then exclusive contracts will have to be brought in. You can't have fighters for a big company (which is I'm sure what Strikeforce are striving to become) travelling around the world putting their reputation and health at risk fighting for another company. It might make sense from a fighters point of view, but in a business sense, exclusive contracts are definitely the way to go.
As for the exclusive contracts being the reason for 'new talent' not signing for the UFC, I don't agree. Even if the UFC had non-exclusive contracts Fedor wouldn't have signed, as the UFC were not willing to bow to M-1 and co-promote. It wasn't in the UFC's best interests to co-promote with M-1 and so Fedor went to a company that would. Then with Jacare, the reason he's now fighting for SF is largely due to their deal with DREAM. He was a DREAM fighter, so it made sense for him to transition to Strikeforce. He wasn't exactly well known, or a big draw at that point either, so it's understandable that the UFC didn't join the battle for him. I'm sure if he came on the market now they'd want him though. Then with Noons, I guess the exclusivity of the contracts does play a part here, as he will have wanted to Box outside of MMA, which the UFC obviously wouldn't allow. So of the 3 examples, only 1 joined a rival company due to the exclusivity of the contracts.
Who have the UFC signed in the last year or so? Roy Nelson, Charles Oliveira, Gilbert Yvel, Yoshihiro Akiyama, Takanori Gomi, Jake Ellenberger, Vladimir Matyushenko, Paul Daley, Vitor Belfort, Antonio Rogerio Nogueira, Phil Davis, Claude Patrick, Cyrille Diabate, Rory MacDonald, Lucio Linhares, Matt Mitrione, Fabricio Camoes, Jacob Volkmann, Ben Rothwell, Frank Trigg, Phil Baroni, Kimbo Slice, Gerald Harris, Mario Miranda, Daniel Roberts, Duane Ludwig, Jake Shields, Karo Parisyan, Sean McCorkle, Mark Hunt, James Toney, Brendan Schaub, Paul Sass, Tom Blackedge, Kurt Warburton, Rob Broughton, Alexander Gustafsson, Antonio McKee, Igor Pokrajac, Darren Elkins, Gabe Ruediger, Edson Barboza, Fabio Maldonado, Travis Browne, Christian Morecraft, Seth Petruzelli, Tito Ortiz and Court McGee. All those guys have made their debuts for/returned to the UFC in the last 12 months or so. There might not be a wealth of huge names in there, but that's a lot of fighters and there are a lot of guys in that list that have put on some great fights. Just because they didn't sign Fedor doesn't mean they haven't signed some excellent fighters and genuinely boosted the roster.