Trulia is NOT a real estate company. No consumer contracts. Trulia does not employ real estate agents, and earned revenue comes from advertising. Trulia is simply an advertising website - yet I completely understand the confusion with the "portrayal" of the site.
The listings found on Trulia, Zillow, and other similar sites, comes from the many Multiple Listing Services throughout the nation, though some agents and brokerages choose not to participate. Why would anyone choose not to participate? The huge possibility of inaccurate information, loss of control of the information, and scams.
To buy a home you will need a real estate professional. Consider asking family and friends for referrals. There's also a "Find an Agent" tab which can certainly help. I recommend calling any agent of your choice, since emails can easily go unnoticed.
So glad you asked the question! Best of luck!