Doctors are in high demand, not just by their patients, but by startups looking to create social networks, marketplaces, and portals around their expertise. Today, HealthTap announced the acquisition of Q&A site Avvo Health specifically to increase the number of doctors within its network, doubling it to 30,000. The acquisition also brings a database of :hundreds of thousands of doctors and dentists across the country,” information that HealthTap previously licensed. The terms of the deal were not disclosed. [Source GigaOM]