Fighters who move outside their talents often suffer for it. Take Edwin Dewees, for example. I find that a lot of fighters that are heavily trained in Gracie-style jits tend to be timid during the opening of a fight, waiting for an opponent to react so they can counter. Dewees, as he showed on The Ultimate Fighter against Gideon Ray, is an extremely agressive BJJ fighter, which is a welcome change. Not only agressive, he's also talented - 27 of his 34 wins are submissions. So what happens when he goes up against Jorge Rivera at the TUF 4 Finale? He strikes. I knew he was in for it when he talked about "working on his striking." Why on earth would a talented BJJ fighter decide to abandon his training and trade blows with someone who has more experience tossing leather?
You might also argue that Georges St. Pierre owes Matt Hughes a debt of gratitude for trying the same thing. Hughes has said in interviews he has a serious jones to put one of his opponents to sleep in stand-up, and he was trying it on Rush in November. Hughes has tried it before, but had the acumen to stop trying to stand and throw when things went pear-shaped; he reverted to the wrestling and grounding-and-pounding that he is justly famous for.
Against Rush, however, he shouldn't have even tried to stand. If Rush was a boxer he might have lasted longer, but St. Pierre is a black belt in Kyokushin and his striking is not only unorthodox (compared to standard boxing) but also includes very effective kicks. I bet Hughes had decided to switch to wrestling after Rush was beating the tuna out of him at the end of the first round. Too bad he didn't try to work his strengths right from the get-go.
"What's crazy about standin' toe-to-toe and saying 'I am'?"
- Rocky Balboa