Asbestos was a very common siding material used in the 1950s. This type of siding is actually known as cement asbestos, as the asbestos is contained within a cement binder.
The risk of asbestos exposure is based on how friable the material it is (how easily it deteriorates). If the asbestos can easily be released into the air, then there is a substantial risk of exposure. This would be the case, for example, with heating pipe insulation made of asbestos.
However, cement asbestos siding presents very little risk and is actually quite durable. You need only to paint it about every seven years to maintain its appearance. And since it's not organic, it will not rot--ever!
The only time asbestos siding needs to be removed is when new siding is going to be installed (never install new siding over material containing asbestos). In this case, asbestos siding tiles can be removed by punching the nails through with a nail set, which will allow the asbestos siding tiles to be removed whole with very little risk of exposure.
Once removed, though, disposal of asbestos siding can be a problem since some municipalities have regulations pertaining to the disposal of any hazardous material. Be sure to check local regulations and practices about removing asbestos siding before taking down your asbestos siding.