Networking site Ryze has paying advanced services: "After several months of offering the free service on Ryze, Mr. Scott decided to start charging a fee for more advanced services. For between $4 and $10 a month he offered various levels of access to both other's people's contact information and the means to search for shared commonalities, such as interests or schools attended or previous companies. So far, "less than 10% of the members are paying." A conservative estimate would give Mr. Scott about $1,500 a month in income from the site."

Ryze is a business network, a bit similar to Classmates.com. One of those great businesses (think eBay) that can create a barrier of entry out of thin air once they reach critical mass.