It's like this: how much content disappears behind paywalls or registration barriers? Google and other search engines don't register! How much content disappears behind format barriers? Google does open some common formats, but not all and not in all variations. How much content disappears behind no-linking barriers? Content in proprietary formats simply don't have links pointing into them - and therefore have poor Google rankings too. The same applies to deep-linking preventers.
Example: those dreadful Flash movies where, sensibly enough, the "Skip Intro" link is inside the Flash movie instead of outside in HTML. And where do these geniuses place such a traversal preventer? Right on the homepage. So every bot already fails at the index.html and doesn't search further. Just like everyone who doesn't have Flash. Or everyone who is, for example, visually impaired.
People, get this straight once and for all: you all have a blind buddy, and that's Google (and its colleagues). Sites with poor accessibility, with JavaScript-programmed links instead of normal links, with too much Flash and proprietary formats - all of that makes life difficult not only for the blind, but also for search engines, which are still significantly blinder. You're not only excluding a population group, you're excluding yourselves from the internet infrastructure (links and search engines). And then you expect sympathy?
Instead of thinking it through and putting the content out there, preparing it and linking it where and how it's reachable for search engines, you'd rather spend vast sums on search engine optimizers to push your meager content up in Google. And then of course you're offended when stupid weblogs simply climb up, just because they work exactly as search engine programmers currently imagine it ...
At Der Schockwellenreiter you can find the original article.