We try to pick people that the members of our community can vouch for - but this is not a limiting restriction. For a student to be picked
he only has to demonstrate that he is able to code, accept criticism and to just stick around and learn. We examine their ability to code/work and provide not just a mentor, but the whole commmunity to interact with, so that we can help them with any problem that may hamper their GSOC work.
We will require each student to start a page on our wiki about their work and have weekly updations. We will also require that the mentors follow these updates and that they interact with each other at least once in a week, via email/irc/video or whatever mechanism is convinient for them. However, we will also try to get the students to stay in touch with the entire community through the mailing list. We will also require them to push their work to a publicly viewable repository so that the community as a whole can review the work.
If, despite these things, a student disappears, or does not work up to his or her potential, the mentor and the SMC organization admins will try to sit down with the student in an IRC conversation or via some other medium to try to see what is holding him or her back and how
he or she can be brought back on track. If necessary, we may need to adjust the goals as originally stated in the student's application, because it is better for a student to do a reduced amount of work than to do nothing at all. If nothing works, we may be forced to fail the student in his midterm or final evaluation, but this will be a last resort, because it will be to everyone's benefit if the student can be brought back on track. If the student stops being responsive, we will require him to report daily on what work he did.
If that doesn't help, then before failing him, we will raise the issue among all the mentors. If there are any doubts, we will also use the main GSoC list for mentors. This is so that we can make sure that the student was not treated/failed unfairly.