I work as an individual, so there isn't a very big team dynamic, but mentoring is still vey important.
Ways I've been mentored:
found a code golfer who was sharing his amazing code on Hacker News, we collaborated on some projects together, and have been part of the growing JS code golf community. He had been mentored before I showed up by another programmer, and in theory I should be turning around and mentoring a new golfer sometime now :D
I know HTML and CSS pretty well, so I hopped onto IRC to see if I could chat and help anybody on there. I have been able to help a lot of people, but I've also found some really caring people who can help answer my questions too, usually about programming. Yesterday one of them took the time to write out a library pattern for me in about 3 different ways until I understood it and I was able to write the code I was trying to write in a better way. I'll make sure to keep helping people in a similar way who have questions I can answer.
I know quite a few designers and developers here in Toronto. We all have very overlapping skill sets, but that also means that we know things that the others don't know. I have been able to "Let me show you this one thing really quick" to show them a tool, technique, or idea - and they're smart enough to see it, understand it, and know how to put it to use. I don't think of them as my 'students', but those little moments are undeniably mentoring in action, just between peers.
So I don't think you need a super formal process, and I don't think it's hard to get started - but I do think it's sorely needed.
Basically everybody should be a mentor. If you're on a learning journey and you've taken a few steps from the starting line, that means already there will be plenty of beginners behind you on the same learning path that you can help, even if you haven't reached 'mastery' yet.