Most of the jobs right now are artsy / techy because those people are easiest to reach from our personal networks and that's where we started signing up mentors. Feel free to throw a janitor in a suggestion box, we'll try to sign one up.
Every mentor is being screened during the interview, but if someone wants to call himself a growth hacker, we are not going to decline him just based on that.
Lifetramp co-founder here. First of all, thanks for the kind words and feedback. We just did a small launch in Poland with mentors that we could easily reach to validate the idea, but we're currently doing what we can with our limited resources (it's a bootstrapped startup) to grow our mentor database as much as possible. Watch this space.
I have posted link to this thread in Polish Startup Scene group, maybe we can help. Getting a work permit in Poland is not hard and Germany is close by.
I'm mostly following people who I met at conferences / meetups / work as well as people who usually have something interesting to say in matters I'm interested in, like people from W3C, Opera, Google, popular UX speakers and such.
I'm sure that's something every average Windows users does as a first thing after they install the system. The point in usability is not having to do these things for common and obvious actions.