The correct number is three and half. 1 x Fodling Bike for city cruising, 1 x MTB for Dangerous Pursuits, and 1 x fast road bike for hurtling past lycra-clad iPhone wielding dimwits on Sundays.
The half a bike comes when your ex leaves with your Downtube, along with the cat and your Dylan CD's, then relents five years later and lets you ride it because you fixed her lawn mower.