You know you're on the dark side when almost all of the dish sized towels in the house have black stains on them.
Oh yeah.

...when you've said "I have enough bikes" and find yourself going to look at a fixed gear. And you justify it because it's *used* so you can't afford not to look at it.

...when you have a ton of laundry to do, you're out of underwear, yet you decide the higher priority items to wash are your bike clothes. The rest can wait.

...you have a chain imprint on your capri pant leg and you think it gives them character.

...you have a 100 degree fever yet commute anyway.

...you have an entire shelf in your cabinets dedicated to water bottles.