As community-built resources become more prominent, so does the questioning of the integrity of information thats available. The pressure has increased dramatically because of the breakthrough popularity of Wikipedia, plus the introduction of similar efforts by Yahoo Inc., the Internets leading destination; Google; and Microsoft Corp. The Internet portals, as they are known, are motivated to do so in search of the almighty ad dollar. An estimated $12 billion is being spent on online advertising this year, which is a double-digit increase from last year. In 2006, analysts think online ad spending will reach $16 billion. To help grab more of this pool of cash, Microsoft, Google and Yahoo each plan to put advertising on their community-built references.As awareness and scrutiny are heightened, a number of incidents are surfacing that call into question these sites integrity. For instance, online encyclopedia Wikipedia, written and edited by users, was stung by high-profile criticism over what turned out to be a hoax entry.Click here to read more about problems of self-policing at community sites like Craigslist. In just one example of how criminals have apparently discovered these kinds of sites, Craigslist, the pioneering feature Google Base closely resembles, was allegedly used to run a prostitution ring earlier this year. While the character of its listings has not been called into questions, Googles been nonetheless pressured to smarten up Google Base. Google faced an embarrassing situation in November when some users were flooded with results from adult entertainment and porn sites, something they specifically had asked not to receive. Editors Note: This story was updated to include comments from a Google representative. Check out eWEEK.coms for the latest news, views and analysis on enterprise search technology.