How is ghost hunting on TV like Baseball cards?

More product, more distribution = a scramble to jump on the niche-wagon., the inevitable saturation point (not if, but when), then a huge drop-off in fans, followed by a sort of re-organization. The few that survive to this point usually have staying power and will enjoy many productive years.

Some examples of the formula:

Beanie babies

Pogs

Flipping houses

Feng shui

Chef-testants

Bobble-heads

Pokemon