Significance

The vision statement of the Wikimedia foundation (who run Wikipedia) is;

Imagine a world in which every single human being can freely share in the sum of all knowledge. That's our commitment.

The sum of all knowledge, free, for every human.

Wikipedia have scale challenges - they're the fifth-most-visited property on the web - but under the hood their technology is comprised of widely-used open-source projects. They use a PHP-driven content system, MySQL databases and lots of caching.

Rather than the tech, it's that vision that makes them the most significant product on the web.

The technical innovation that companies like Google and Twitter have achieved is staggering; Indexing all of the web's content and making it searchable in milliseconds, for example, or operating a global real-time communications network.

Incredible technology from behemoths that were once tiny startups.

A USB memory stick isn't cutting-edge technology, but the whole Korean-language Wikipedia is just over 1Gb zipped, and fits nicely on a memory stick which can be attached to a balloon and sent over North Korea, sailing over the firewall on the breeze. Wikipedia makes this kind of vital information activism possible.

Sometimes it's not the tech that makes the startup: it's the vision.