House Party hosts tend to spend $100 to $150 of their own money on food and offerings for their guests -- more than the value of the freebies they receive, Perry says.
For guests and hosts, the chief motivation is to sample products and provide feedback, says Selin Malkoc, assistant professor of marketing at Washington University in St. Louis.
"For instance, moms would like to give feedback on baby products because they are very involved in this category," Malkoc says.
Jessica Kovach of Greensburg, Pa., has hosted five of these events. She says she sends invitations through the House Party website so guests find out the product focus. "I don't push the products," she says. But because she hands out samples and coupons, and some activities revolve around the product, the message is there, Kovach says.