From the excellent Simple Bees site, Swarming Bees are Healthy Bees is an article that first appeared in BBKA News.
"Beekeepers are constantly being directed to control swarming at all costs, whether to improve honey harvests or reduce nuisance to neighbours. I have been wondering if a century of increasing control over honey bees’ basic natural function has had an adverse impact on the health of our bees." John Haverson