The video interview in the above link is particularly cool.

Hadoop seems to be the quasi-secret sauce in a number of projects.

A comparison between Hadoop and Google's Sawzall is at: http://glinden.blogspot.com/2007/04/yahoo-pig-and-google-saw...

The NLP search engine Powerset also uses it. http://blog.powerset.com/2007/10/16/powerset-empowered-by-ha...

Looks like Yahoo! can now refresh its entire data base 34% faster. Meaning its index will now be overall updating more often than google. (although google is still the king of indexing content on a 'rate of freshness' scale')

(note: I am trying to be funny)

well what is java written in? you can always claim that hadoop is ultimately writen in the language used to create java.

they should have used Perl5 and Moose thought!

Java is written in mostly Java, of course !

According to sloccount of latest tar of OpenJDK6:

java: 2393565 (72.63%) cpp: 462235 (14.03%) ansic: 419499 (12.73%) sh: 17089 (0.52%) asm: 1936 (0.06%) awk: 598 (0.02%) lisp: 449 (0.01%) cs: 72 (0.00%) jsp: 24 (0.00%) csh: 3 (0.00%)

There is lisp in there? I am betting elisp for an emacs major mode or something. But 72% Java. c/c++ would be for posix interfaces, and probably enough core VM code, and perhaps hotspot stuff.