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Blogging contests will only be successful if they are promoted well, have good prizes and have very rigid and well defined rules. As Tom mentioned you'll get extra content for your site but you need to maximise the number of links you will receive too. For Example: If you are an e-commerce website you could invite bloggers to imagine they have $500 and for them to write a blog post on their site about the products they'd buy with this money and many will link to the products. The prize could then be the $500? You want to make sure that if the blogger is going to write a guest article for your site that they also write an article on their blog promoting the blogging competition. You can give out extra prizes based on social measures such as the article that gets the most  FB shares, +1's or Tweets that the article receives.

Just as Ressler Motors said, there are many MANY factors to take into consideration when you are looking at a websites ranking. I must admit, SEOMoz does a great job with their different metrics, and they can be very helpful... But even so, big G uses literally hundreds of triggers to determine any individual ranking. So, really you should study lots of metrics for both websites - anchor text usage to target page, brand links to each homepage, title tag usage, page load times... and lots more! Hope that helps!

How do you plan to build an audience ahead of time to promote your documentary programme? What are you expecting back from the time, money and energy you have to invest here? Get some partners. Get onto the social platforms of other british political commentators and use their already developed communities to promote yourself

Looks like no one has an answer to this question. It is probably too early to assess the impact of Google Plus on SEO.

Link from within the text of the lens. Place the text link as high as possible, ideally in the first text box.

Like anywhere now, there are black hat sites / directories and white hat of the same.  Typically, if the links from China are similar to a linking scheme you'd see anywhere else, it's best to avoid the possible short term benefit you'd get in going after those links.  Although you probably already have, I'd continue to look for link opportunities from the first ten listings instead of this one.