Twitter's idea is not obvious. Why would restricting blog entries to 140 characters result in a new and very interesting phenomenon?
Larry and Sergey's PageRank isn't a new application level idea (as search engines already existed) but rather a better implementation of an existing application level idea.
The 140 character feature is definitely an execution issue and not an idea issue. It wasn't part of the original design, they iterated their way to that.
"@Jack was still just an engineer, and the service was only a few months old when the group acquired Twitter.com and re-branded. Back then, we had no character limit on our system. Messages longer than 160 characters (the common SMS carrier limit) were split into multiple texts and delivered (somewhat) sequentially. There were other bugs, and a mounting SMS bill. The team decided to place a limit on the number of characters that would go out via SMS for each post. They settled on 140, in order to leave room for the username and the colon in front of the message."
Twitter's key insight was to extend a blogging platform to mobile phones (hence the 140 limit). It was definitely innovative and smart, but not the kind of thing they give out Nobel prizes for. I think the Google boys' idea went much deeper, and their indexing methods were completely novel at the time, hence much more relevant results.
Well, that's a matter of opinion. From what I have read, their method was innovative, hence the patents. The problem with working this kind of stuff out is that history is always biased towards the winners (in the sense that nobody talks about the losers). With that it mind, you could quite possibly be right.
If not their methods - their hardware was definitely a new thought at that time - Low cost commodity hardware etc; when it was cool to spend 10k on a server,
Larry and Sergey's PageRank isn't a new application level idea (as search engines already existed) but rather a better implementation of an existing application level idea.