Re: What, if any, are the benefits of spiders to our society?

It is often difficult to place a given organism in to a category of usefulness to society. Nevertheless, spiders are quite important in relation to the well being of society. Spiders are numerous enough in agricultural fields (sometimes literally thousands or millions to the acre) that they serve to dampen insect numbers, often including pest species, because these are often the most common insects. The world wide benefit of pest control by predatory insects and spiders together may exceed US $100 billion per year. Spiders are also important in natural systems as secondary consumers, again keeping insect numbers in a reasonable balance most of the time. In this modern age of bioengineering they may also provide raw materials for new generation pesticides based on their venoms and new drugs and textiles based on venoms and spider silk.

In addition, in some societies, spiders are considered as good food items!

References:

Baskin, Y.  1997. The Work of Nature: How the diversity of life sustains 
     us.  Island Press, Washington, DC.
Gertsch, W. J. 1979.  American Spiders, 2nd ed.  Van Nostrand Reinhold, New 
     York.
Menzel, P., and F. D'Aluisio.  1998.  Man Eating Bugs: The art and science 
     of eating insects.  Ten Speed Press, Berkeley, CA.
Wise, D. H. 1993. Spiders in Ecological Webs.  Cambridge Press, Cambridge, 
     England and New York.