Personally, I tend to agree with benszeto that a public platform may not be an effective “mentoring” session, but rather a social interaction, i.e. getting career advice in a particular industry, etc. If there’s some database / place that juniors can post looking for some guidance or “expertise” advice in an area, it maybe of some use. Vice versa, seniors that have certain experience and skills posted in which juniors can approach them. 🙂 Just my two cents worth here.