1) We automatically scan the blog feeds for creative commons licensing information, and if the license is missing or specifically denies commercial use we publish an extract of the article and a link to the original blog posting. Plaxo does NOT do this at all.
2) We never show advertising against a blog post, the rights to commercial exploitation of content rests with the site that originates the content, Plaxo is taking liberties with peoples copyright by showing Google ads that earn them revenue against each blog post, many folks rely on professional revenue from pro-blogging to provide an income.
3) Plaxo invites comments on each post which it shows against the listing, but unlike fav.or.it, they don't post the comments back to the originating blog, Plaxo is basically fuelling thier engagement on other peoples content, without contributing anything back to the originator.
Poor show plaxo, you should sort this out!!!!.