Well, a person can meet some but not all of the diagnostic criteria of any illness - to the aforementioned point, these disorders are usually diagnosed when the disorder significantly disrupts the patients life - jobs, friends, other social functioning, etc. Of course, if the symptoms of any condition were to advance a person's life, it could never really be considered an illness.

I don't think that anyone was trying to trivialize any illness, and its apt to note that OCD quite probably is related to the quasi-obsessions of which the original poster speaks, although on a massive, overgrown, and uncontrollable scale. Also, you are quite right, imo, to mention that OCD is quite terrible as, in most cases, it very dramatically prevents the sufferer from living a normal life, and can be quite sad to witness. Fortunately, psychologists are now making advances in cognitive therapies to augment the more traditional behavioral methods that have shown success, and psychopharm researchers have shown treatment efficacy using the relatively safe SSRI class of antidepressants.

  -Adam