Unless you have fruit trees or grow things like squash/melons/cukes/berries...and tomatillos for some people...it's not needed for the most part, fwiw.

Many garden fruiting plants pollinate just fine by themselves...some are so bred to mutant-levels by humans via selection over years (centuries) that the flowers self-pollinate readily before the flower is even fully open (especially peas and beans).

GW does have a "bee and beekeeping" forum, but it's not used much at all.

http://forums.gardenweb.com/forums/bees/

There are gardeners and home fruit growers who do exactly what you suggest-keeping honeybees to improve pollination. Here in Madison, WI, urban beekeeping is in the news recently, and it seems to be growing more common. I looked into it several years ago, and I even picked up a book on the subject. After a few months of reading and looking at equipment, I decided that this is an expensive hobby, and that it would take me something like 10 years to pay for the start up costs. If you have your own meadow, or you live near an appropriate meadow, full of flowering plants, from April through September, then it might be worth it. We have several different species of native bees in our yard, and I help them out by not using toxic chemicals in the lawn & garden. Also, we have something flowering here throughout the growing season. Pollination is usually not a problem for us. Beekeeping is an interesting hobby, and I may yet take the plunge.

It is not necessary to have an orchard or grow a lot of the cucurbit family to have a bee hive or two and many backyard gardeners are putting them in. If you do be sure there is a wide selection of pollen sources available, including the wild flowers many people think of as weeds. Also be sure you do not have neighbors that indescriminately spray broad spectrum poisons around since those will make keeping bees more difficult.

And check with the local authorities - not always legal.

And if they are legal, often guidelines to follow as concerns distance from the property line.

That said, a clean garden with minimum pesticides used invites all sorts of beneficials, honey bees and bumble bees among them.