I think training can be a bad thing when imposed on young learners. The kids who grow up with a passion to play take short cuts in their musical education to faster acheive the sound they want to hear but their passion usually overcomes any technical shortcomings. I'm sure some of the people who've made a living in the music business probably had to go back over and take some formal training to reach another level of understanding and enable them to better share ideas with other musicians. Those same players may have had their talent stifled at an early age had too much attention been paid to the musical theory.