It seems that EA was trying to sell the newest Dragon Age 2 DLC via in-game instead of through Steam, which is a violation to Steam’s terms, this has caused Steam to remove Dragon Age 2.
Unfortunately, Steam has adopted a set of restrictive terms of service which limit how developers interact with customers to sell downloadable content. No other download service has adopted this practice. Consequently some of our games have been removed by Steam. – David DeMartini, EA Senior VP of global electronics commerce.