There’s quite a debate going on on whether and if so, how, to standardize a PATCH method for HTTP. James Snell, who edits the draft spec, has a list of links to posts that make up the discussion.
I’m unsure I’d be happy about a PATCH method; my main gripe with it is that its semantics heavily depend on the content being sent (which needs to be some sort of diff format matching one of the resource’s representation formats). Right now, I agree with Dare Obasanjo:
If a field is important enough that it needs to be identifiable and editable then it should be its own resource.