William Jacobson at the Cornell Law School writing for the Legal Insurrection blog:

King & Spalding dumped the House of Representatives as a client in DOMA litigation after coming under threatened protests and boycotts by groups opposed to DOMA.  A key aspect of the threats was that protesters not only would protest King & Spalding, but would go after other King & Spalding clients which had nothing to do with the DOMA case. That, apparently, was too much for King & Spalding to bear, so it threw the House of Representatives overboard. King & Spalding may have started something it cannot stop.

... King & Spalding, like many seemingly powerful large law firms, actually is extremely vulnerable once it becomes known that it will give in to political pressure. ... It just so happens that almost every state in the country has either DOMA constitutional amendments or DOMA legislation, including Georgia:

When attorneys put business convenience ahead of the attorney's duty of loyalty to a client, there is no good outcome.