Since then, a majority (although not by much) of the ethics committees that have considered the issue has found that the practice is not improper. In addition to North Carolina (Ethics Op. 2011-10) and South Carolina (Ethics Op. 11-05), Nebraska (Ethics Op. 12-03) and New York (Ethics Op. 897) have approved the practice. I commented on (and linked to) the NY opinion last January (here).
Maryland is now the most recent jurisdiction to have approved it. The Maryland State Bar Association Committee on Ethic recently issued an opinion holding that the practice is not per se prohibited as long as the lawyer takes steps to ameliorate potential ethical concerns that may be implicated by such arrangements. See, Maryland Ethics Op. 2012-07.
In contrast, three states have issued opinions disapproving of the practice: Alabama (Ethics Op. 2012-01),
Indiana (Ethics Op. 1 of 2012) and Pennsylvania Ethics Op. 2011-027 (2011). I reported (with links) on the Indiana opinion here and on the Alabama opinion here.
For more information you can go to the ABA/BNA Lawyers Manual on Professional Responsibility, 28 Law. Man. Prof. Conduct 600.