There is thin grey line separating Obession and dedication.
The latter can lead to the former which is usually considered a bad thing, although the subject of obsession does have an influence.
For me the nearest I have come to an obsession was my fan dedication to various TV shows, but compared to some I was relatively tame. I have been to a single Doctor Who convention in 2000 and it was certainly an experience, while there was a small percentage of cos-players in the crowd (admittedly many of them choldren) most people were quirky but nothing worrying. However there were a few who were a bit of your stereotypical sci-fi nerd and while I am sure they were perfectly harmless I did feel a bit uneasy. … but not some much as the guy dressed as Jamie who took the Kilt tradition on board. I do believe Frazer Hones made the costume department put weights in his Kilt incase of wind on location… it was a windy day in Coventry and the chap had not heeded that advice.