Obsession has come to have a positive connotation. Individuals and companies brag about being obsessed about this or that. But obsession is a psychosis, and the original meaning of the word is still valid.
Obsession, according to the canons of psychology, occurs when an innocuous idea is substituted for a painful one. The victim simply avoids recognizing the thing which will hurt. [source]
Obsession with small things is a way to avoid thinking about big things. Maybe our company is sinking like a rock, but our web site is valid XHTML 1.1! Maybe my relationships are falling apart, but I’ve almost got all my GTD applications configured the way I want them. Maybe my paper makes absolutely no contribution to science, but now I’ve got another publication.
Paying attention to detail because it is important is not obsession. And when people brag about being obsessed, they’re probably trying to imply that this is what they’re doing. Details matter in relation to a bigger picture. Focusing on details in isolation, hoping that the bigger picture will take care of itself, is obsession.