Your precision concerns sound familiar – I work on this technology for place recognition in mobile robotics, and one wrong match can irrecoverably corrupt the robot’s map, so we’re also very focused on getting near-100% precision (though we’re less concerned about recall).

The font problem I think isn’t too severe – One decent solution is to detect text patches and use a less local descriptor for those image regions.

The “Dummies” issue is certainly harder. I face a related problem in place recognition in that many places share repeating features such as brick walls. (See here). Our solution is to learn a generative model of the image data so that we know which parts of the image are distinctive and which are common. We learn correlations between sets of features also. I’ve found it to give excellent results, although the largest index I’ve worked with so far is about 100k images.

The hardest case of detecting Bluray DVD vs regular DVD is really tough – I think probably beyond the abilities of current methods.

Not sure where you got the 5.5 million number. Its currently 2.5 million and increasing.

We do a lot of things to improve accuracy. The iphone has one of the
relatively better cameras for a phone. Many of them are a lot worse and the goal was to make it work with virtually all of them. Blur is
one of the really bad things that can happen. We have to achieve a very high precision at 1 – most researchers look at precision at 3 or 5 but for a mobile phone there isn’t enough screen
space to display multiple results. At the accuracies we are operating
a 1% gain in accuracy is a big win (a 1% difference translates to 10
queries out of a 1000) and usually paid for in terms of latency.

Latency. Most of the latency occurs outside our server and its not
clear why its happening.

In terms of recognition, the Dummies problem you mention is a difficult issue. A substantial portion of many of these covers is identical and in the case of the Dummies series there are about 2000 covers. The problem is complicated by the fact that there are
variations of this problem where the differences are even smaller
- eg Bluray DVD vs regular DVD and the difference is just a small
piece of text. The system doesn’t know whether the query was
the portion of the book that was common or the other portion
We are working on this and hope to resolve it in the future at least
for the Dummies case.

The font problem – some of this will hopefully go away in a future
version.