PROMYS Updated +Created
The good:
The bad: everything else. Closed source learning materials + a university-like selection program. Such a waste of efforts that could benefit way more people with more open resources.
meta.mathoverflow.net/questions/4889/request-to-keep-an-eye-out-for-promys-admissions-problems asking to remove PROMYS problems from MathOverflow. And it seems to have been mostly accepted. Newbs. Any maths problem should be allowed to be askeable online. There are no fundamentally new problems, copyright takedown is just silly.
Terence Tao Updated +Created
The cool thing about Terrence Tao is that besides being a mathematical genius, he is also interested in modern technology such as formal proof systems (notably Lean), automated theorem proving and forum-like collaboration as in MathOverflow[ref]. For that, huge kudos.