Joy to the WorldResearchers have found that happy people tend to "cluster," which is to say that in a given population you are more likely to find happy people in groups than singly or in association with unhappy people. The researchers interpret this as indicating that happiness spreads socially: your happy friends make you more happy, their happy friends make them more happy, and so on.
Of course, there's another possible interpretation here: that happy people are happy because they are in groups -- they have a strong set of social connections -- so that happiness is an effect rather than a cause. It's also possible that there is correlation without causation: happy people are more sociable because they're happy, and therefore are more likely to form social connections than their depressed, unhappy fellows. But let's not go there. For now let's simply go with the researchers in believing that happiness spreads via social bonds, and that online communities are therefore virtual happiness engines.
Yay us! We make the world happy!