Actually if you look at it that way there are quite a few... In the year 2000, there were 76.6 million students enrolled in schools from kindergarten through graduate schools (Wiki) In 2009, there were over 6.2 million teachers in elementary and secondary schools (Wiki) Just guessing, maybe 5 to 10 million blackboards in THE US ALONE. And you'd have to figure like a PC you never just have 1 for all that long and software & support are also involved. Of course that doesn't count the corporate world. Frankly, from Cisco's commercials with a Doctor dispensing meds over the internet, you'd have to think someone will take them out at some point as this seems a simpler concept, maybe not though.