I'd say that the level of fanaticism can be pretty high in many of the examples I used. F1 fans travel all over the world, dress up in funny costumes, and parade around carrying massive flags showing which team or driver they support. Google "Tifosi" for a flavour.

Lego fans do things like build this 46' self-supporting bridge http://gizmodo.com/5272536/46+foot-long-self+supporting-lego-bridge-to-set-new-world-record.

Each of the other have their own version of fanatic behaviour ... my favourite for sheer lunatic fun remains the annual Bloomsday celebration of Joyce's Ulysses.