"Thus," it continued, "online community members are unlikely to offer actual financial assistance, such as a loan or a gift of money, to community participants when negative outcomes occur as a result of their financial decisions."

A moderating influence on a community member's risky behavior is how active they are within a community. If a member isn't very active in the community, they're less likely to engage in the riskier behaviors of active members, the study found.

The researchers looked at three settings.

One was Prosper.com, a , which has 1.11 million members and has created $249 million in personal loans. After tracking a group of 600 Prosper members -- some in communities, some not -- the researchers found that, over an 18-month period, community members engaged in riskier financial behavior than non-members.

Another setting was eBay in Germany. There, for 22 months, the researchers studied the behavior of 13,735 customers with an interest in collectibles -- stamps, coins, books, art and toys. Again, they found riskier behavior by community members compared to non-community members, as measured by the number of bids placed on an item and amounts paid for an item.