This is an experiment to highlight the dependency of the V-Measure value on the number of clusters of 2 independent uniform labelings for a finite number of samples.
Intuitively it seems that for finite number of samples the V-Measure is victim of some kind of birthday paradox that naive users might not be aware of.
Even if the maximum number of clusters considered (e.g. 10) is small with respect to the number of samples (e.g. 5000), the V-Measure of 2 independent uniform labeling is still noticibly increasing with the number of clusters in at least one of the labeling.
Careful counting number of possible combinations is required to be able to come up with an adjusted for chance variant of V-Measure that would counter this effect.