This below post goes on to say that this type of marketing isn't all that measurable - and so you can't put a good metric on it. This then is a bit of a guerilla scene. But one which some have used successfully to increase their list.
» Comment and Community Marketing - Social Media Optimization: "Comment and Community Marketing
I have noticed the appearance recently of two “new” social media marketing terms; Community Marketing and Comment Marketing. These new labels seem to be used interchangeably with conversational marketing.
While conversational marketing is part of an overall marketing philosophy and strategy, community marketing and comment marketing appears to be simply a tactic that you would use.
For those unfamiliar with the terms, community marketing refers to the tactic of engaging customers in online communities. These communities can either be hosted by a brand or can take place on 3rd party sites. Comment marketing is a tactic used on blogs, forums and sites like Yahoo Answers."