Tallon - 10:29 pm on Dec 1, 2010 (gmt 0)
but note that Google did say they take the authority of the posting person into account.
Right...but if you're regularly doing "giveaways" and "contests" that incorporate retweeting, facebook "likes" and "friending" and subscribing to twitter accounts, etc., it wouldn't take long for you to have an "authority" twitter or facebook account (due to all the signups and retweets and facebook likes to get in on the freebie giveaway).
There's some really creative promotions going on that used to say: link to this post from your blog or website and you'll get an extra entry...but that stopped (due to fears of incentivized linking probably) and moved toward "link using your twitter and facebook accounts". It's a great way to build buzz that's for sure and I've seen sites get a tonne of links, tweets, retweets, etc., and thousands of new subscribers using this method.
Another thought: what about blog badges or site badges? Some sites in my niche will link out to another site and offer a linked badge for the link(ee) to add to their site (saying something like "as featured on siteabc123dotcom)...it's totally voluntary with an unspoken understanding that those who do add the badges to their websites will be more likely to get more links in the future.
There are a lot of things a person can do to generate some (manipulated) buzz and build authority accounts, I'm just really unsure of what's ok and what isn't ok or what's ok now won't be ok in the future.