I've mused about this before, but I thought it would be good to put it to a poll this time. The discussion before was absolutely fascinating. Many folks saying that it's our ethical duty to inform clients of our true opinions, and that part of the value of what we provide is those opinions. Many folks saying we should take the work and do it, as it's not our job (or expertise) to judge business ideas (e.g. do you want your hair stylist to refuse to give you the haircut you want?).
Note that I did not include an option for "it's complicated" or "it depends". I'd rather just see the final judgment call. Poll is in the sidebar, and you can discuss below. RSS readers have to make the jump over to the site!