What fraction of laptops and desktops have built-in [video] cameras?

I don’t see how anyone could give an accurate percentage on this with the vastness of the market. Apple computers are easy to compare and generate stats from because they’ve got such a relatively small range of products, from one company. Bring into the equation windows PCs with vast numbers of choices from many, many manufacturers and it gets difficult.

Also, why does it need to be built in? I imagine there’s a lot of people out there with external webcams they’ve bought separately.

Try all macs with a built-in screen (since 2006) have cameras.

As for the other manufacturers, I would recommend visiting each site and looking into which models offer webcams. Keep in mind, that many people will not add it as an option, so I would count 2 statistics: percent of computers that can have a webcam, and those that are guaranteed to have a webcam.

Keep in mind the many manufacturers to buy from:

Dell
HP
Fujitsu
Acer
Gateway
Sony
Hitachi

While it isn’t in the scope of the question, you may also wish to look into any published stats on external webcams.

If I had to put a number (guessed) on the number of computers with webcams, I might guess 30%. I’m probably wrong.

Does your program use the webcam as it’s core functionality, or is it a supplementary feature?

damien: it needs to be built in because people would never connect a camera just for this little application.

blastfamy: yes, core functionality…

This may be one of those things that must be guessed at rather than measured :(