What ever the arguments for Facebook, being on the worlds most dominant social network cannot hurt. For one this gives you an additional channel out there on the wild west of the web which never hurts in the publicity stakes.
What having a Facebook page gives you is another shop front on the web. You may already have a website but its unlikely the website will have any capacity for social interactions. So adding your business enables you to reach a audience in order to have a social conversation.
Having a Facebook page opens you up to the metrics and services that FB offers such as knowing what your customers like through the innovative “like” mechanism. FB lets you garner whole reams of information on visitors and this might be new information compared to the standard webstats on your average webhosting package.