two and a half.
One is my road,
One is a mountainbike.
One is a track frame being built up.

Obviously I think I have full right to own multiple bikes since they are being used in different manners.
Also, I don't care if someone has 20 bikes. that means that's a load of money being spent on something better than car expenses.
I also think that owning more bikes means you are more of an enthusiast. Collectors don't use what they collect. Collecting means buying and putting them on a shelf.