The technology is widely used - more than 100,000 Web sites use the technology, the companies say. And it's largely effective because the images - which are scans of archived newspapers and old books. You see, it's the graininess of the letters - cracks and so on - that makes it hard for computers to read. From the Google post:
Computers find it hard to recognize these words because the ink and paper have degraded over time, but by typing them in as a CAPTCHA, crowds teach computers to read the scanned text. In this way, reCAPTCHA’s unique technology improves the process that converts scanned images into plain text, known as Optical Character Recognition (OCR). This technology also powers large scale text scanning projects like Google Books and Google News Archive Search.
And there you have it - the 2-for-1 that comes with this acquisition. Google becomes the provider of a security technology that's widely used, widely recognized and apparently pretty effective. At the same time, the company also scores the technology that will enhance its book and newspaper scanning process.