i watched a neighbor'* car go up in flames from a leak that went un-fixed... the oil kept dripping onto the exhaust manifold, and one day, it just lit right up
and then the battery exploded, the fire department came, and the entire engine compartment was junked.
anyway, depends on where it is. you can get away w/an oil pan leak w/o too many worries, but honestly, most of the leaks aren't nearly as bad to fix as what you might think. the oil pan didn't take long at all, with a set of ramps to work under (i'm sure a good set of jack stands would make it just as easy). threw in some mobil 1 when i was done, and haven't looked back - no more leaks!
and the motor LOVES the mobil 1... nearly constant pressure, at temps between operating range and -5 degress. gotta love it.