As investors bet on the future of social networks, some of the biggest players in the field are due to unveil this week ways of piping in advertising to the most personal of media formats.

MySpace, the world's largest social network, is releasing on Monday details of how it is building discrete audiences out of nearly 110 million users worldwide in a format it calls HyperTargeting.

Smaller but rapidly-growing rival Facebook is expected to disclose on Tuesday its strategy for serving advertising in and around the personal pages built by more than 48 million users.

And BuzzLogic, a privately-held marketing technology firm, is opening up its system for linking advertising to blog discussions and chat forums to public testing.

Most of the announcements revolve around the Ad:Tech marketing and technology conference in New York this week, in which scores of companies will exhibit techniques for delivering commercial messages to consumers who now split their time between a growing number of media outlets.

But the discussion of who can best reach audiences online bears greater weight this year following more than $10 billion spent on the largest Web advertising firms by the likes of software maker Microsoft Corp and, pending regulatory approval, Web search leader Google Inc.

MySpace said more than 50 advertisers have joined its HyperTargeting program, which mines the information on the social network's member pages to determine their main interests and what kind of commercial messages they would respond to.

It's looking at what they say, what they do and what they say they do, said Adam Bain, executive vice president of product and technology at Fox Interactive Media, the parent of MySpace within Rupert Murdoch's News Corp.

It's not keyword-based, so they don't have to mention Tom Cruise for us to know they're a fan, Bain told Reuters. We're smart enough to understand the movies they list have Tom Cruise in them.

MySpace began by identifying audiences in 10 major categories, such as music, travel and sports, and is now creating 100 sub-categories within those groups. The aim is to narrow down audiences so far as to distinguish a fan of romantic comedies from one who prefers satire or slapstick.

Advertisers already using the program include Procter & Gamble, Ford and Sony Electronics. MySpace will also announce tools for small businesses to create ads and deliver them to relevant audiences on its network.

It estimates that anywhere from 5 million to 10 million independent vendors and businesses already use the social network.

In a separate announcement, BuzzLogic will make available a tool that identifies influential blog and social media conversations about products or related issues and lets advertisers immediately place an ad on the Web page where the discussion is taking place.

For the first time we're enabling advertisers to do conversation targeting and focus ads within conversations. BuzzLogic Chief Executive Rob Crumpler said in an interview.

Participants involved in private tests of the system include Wharton Executive Education and marketing agency Publicis.