It's inevitable that text links will, at a point in the not too distant future cease to be relied upon to the degree Google and other engines place on them currently because of clear and obvious abuse. In 2003 it took just 32 external text links to get George Bush's Biography site to rank at #1 on Google for the keywords; miserable failure & failure which really highlighted how easy it was to "influence" Google data. It's been widely known for a very long time that links assist rankings, links can be bought and it just boils down to the depth of a pocket at the end of the day. Everyone knowns about it and so does Google, which is why it's been above radar at GooglePlex for years. PR went the same way. Cracking idea at the time until Google realised shortly afterwards that PR too bore an un-healthy relationship between rankings and the depth of an individuals pocket which forced Google to look into ways of identifying sites believed to be blatantly selling PR for the sole purpose of artificially inflating other site rankings. It's not just organic listings they've been looking at in detail, since last July they've been hammering away nicely at Adwords abusers. At the end of the day, sites that are 'solely' reliant upon links for their rankings may be in for a surprise. My 2 cents worth.