It has WiFi, which requires FCC testing for the US market as well as compliance certificates for the European area. These certifications and checks are f...ing costly.

RPi/Arduino in contrast only have wired or no networking, thus eliminating a huge part of the upfront costs (e.g. in Europe you then only need a CE certificate, which you can either issue without testing and be liable if your module doesn't meet the standards, or you get an ESD/EMR test for a couple thousand bucks).

Tessel is marketed as a "micro-controller" while the PI as a "micro-computer".

Javascript marketing aside,it would be interesting to know if one can reproduce all Tessel capabilites with a Pi + extensions.

I dont think the "but it runs nodejs modules!" matter that much,if you're going to write for embedded devices,you need to go low level and seek optimizations like crazy.The stuff has like 32MB of ram,you cant do much in javascript+nodejs with that.AFAIK it doesnt even run a javascript engine,but translate the code to LUA.

Equally as ill-conceived and/or misdirected as other "language du jour"-specific chips of times past?

http://en.wikipedia.org/wiki/PicoJava

http://en.wikipedia.org/wiki/Jazelle

Lower barrier of entry for people interested in playing around with hardware development. No breadboards and wires, only pluggable modules. Javascript instead of C.