So if we hardly knew they existed why do we want to encourage them into our gardens? Well, with the current crisis with the honeybee population (number are dwindling because of pesticide use and disease) we stand to lose more than just honey. Bees are one of the major pollinators and without pollination most plants are not able to produce fruit, vegetables, seeds, and new plants. Basically, no pollinators=no new plants.
Thankfully, native bees are great pollinators and encouraging them into the garden is a safe (and now fashionable!) way to maintain a healthy and diverse population of native pollinators!
Check out sculptor Greg Corman's blog to see more examples of his beautiful Native Bee Nests (all hand-made from Recycled Wood and Steel) and to learn more about why native bees are so important: http://www.zenindustrial.blogspot.com/
You can also check out this great article on California's native bees for more info: http://www.orionmagazine.org/index.php/articles/article/2869/