Too Long; Didn't Read
Everybody loves the concept of mentoring. You will both help your padawan and clarify things for yourself. Maybe you will also get a promotion for such activity. So, there are no drawbacks at all and if you have a chance, you should try it. But hard-hearted senior developers usually forget: a junior is shivery and vulnerable. He is almost like a child who needs to be taught everything in this unfamiliar world. And his further career depends a lot on his mentor.