Ick, Good thing these are both MLDs or else I'd be dialing up Friedman's office myself. Rivas was "meh" at best during his days as the Twins' Starting Second Baseman/Shortstop, decent glove but not enough "pop". He eventually got beaten out of his job by Jason Bartlett and Nick Punto in 2005. He could have been signed as a stopgap between Lugo and Upton, if a Lugo deal is near finalization. That's just my theory.
As for Camp, he was a KC Royal and that is about the most positive thing I can say about him. He could prove to be better than advertised and been in the wrong position in KC's past bullpen....but that's the best case scenerio for Camp.