Personally I don't think it should be compulsory as there are some people who REALLY do not like these sort of manouvers, however it (AND aero's) SHOULD be strongly encouraged, especially foranyone who is intending ANY sort of career in aviation.
Spin trainig should be done in a suitable aircraft, teaching in C150's and most Cherokees tends to be rushed because the spin will often degrade into a spiral dive and so is not really good spin training, IMHO the best aircraft is the Chippie or the DH82a - also the Tomahawk spins well, but DON'T look back at the tail while you are doing so!