Diigo does a pretty nice job of highlighting. I don't publish my highlights but a lot of other people do.
Socialbrowse might address something I find a bit annoying about Diigo: I don't care what most people think about an article, especially if I don't know the commentators. The highlights of others just clutters my page most of the time. Diigo allows you to turn page Highlights off but ALL Highlights are removed including my own...
Search engines were pretty crappy before Google (and there were plenty of 'em-- it was a crowded market).
There were lots of crappy mp3 players before the iPod.
Cell phones were pretty universally crappy/boring before the iPhone.
A guy I know who was a VC in the first bubble laments that he funded a startup that did the EXACT same thing as YouTube and failed horribly.
Timing and execution can turn an existing market on its ear or develop previously small/uninteresting market. And by looking at the previous failures in a market, you can actually learn a little bit about what people really want or don't want (on someone else's nickel).
In short, don't dismiss a market because someone else failed trying to serve it.
Many of the modern web successes have shadows in the 90s, I don't think that should hold anyone back. The changes in internet culture and technology, as well better understanding what people want means a lot of old, failed ideas could work someday.
I reckon there's been a lot of different apps that do in-page commenting, but they didn't have the social infrastructure to make it stick. I think socialbrowse has the right approach because the comments and link sharing complement each other.
Agreed, I've lost count of the number of apps that have tried this over the years, probably all let down by not getting the social aspect right: lack of community/friending/critical mass.
The idea always seemed to make sense, just waiting for the right time and the right implementation. The friending/link sharing angle could be the twist that makes it work.
BumpIn.com is also doing the same. But I think that the market size is very big. Being able to comment and interact with other people on any site is the missing feature of web 2.0.
In this case that multiple players can exist together. But sooner or later something like browser wars will start.
