There are many ways of classifying the various types of cyclist, but one in particular separates people into two clearly defined camps: those for whom one bike is plenty enough, thank you very much, and those we might call serial bicycle buyers.
Like a branch on the evolutionary tree, members of the latter group begin their cycling life in the first faction, but are one day struck by a realisation, usually while in a cycle shop or poring over a magazine advertisement: "Hang on – I could buy another one."
For me, the defining moment came around eight years ago, when a silver-tongued sales assistant raised the notion that my elderly, rigid-framed mountain bike, till then used for all riding, both on and off road, was a bit outdated, and guided me gently towards a rack of gleaming new models.
To my slight shame, I now own four bikes, something that mystifies not only non-cycling friends but those, my girlfriend among them, who happily make do with a single bike. To me, it makes perfect sense: I have a mountain bike, a road bike, and an older, slightly scruffier bike I use for commuting and leaving locked up around London. The fourth, a single-speed machine fashioned from an old road frame, is perhaps an indulgence, but it is at least on long-term loan to a friend.
I have also met many worse cases, people who have entire rooms in their house filled with bikes, frames and the assorted components of half-finished "projects".
Such habits raise a series of questions, the most obvious of which – where do you stop? – is a popular one on internet cycling forums. One oft-repeated answer is that the ideal number of bikes is X plus one, where X is the number you currently own.
The other debate is more obvious still: why? Isn't it an indulgence? To an extent, yes, but my argument would be that when set against many other leisure pursuits (classic cars, yachting, cocaine), cycling is absurdly economical.
The New York Times motoring column recently published some apparently back-of-the-envelope calculations about the relative costs of running a car and a bike, and concluded that cycling costs an average of about $390 (£240) annually, even spreading the purchase price of the bike over a series of years.
If it's that cheap, I could always get another one.