If you love to code in Erlang and read Japanese..

Please watch out http://ja.doukaku.org/lang/erlang/unsolved/
There would be many challenges to solve in Erlang programming language.

(added: In English, you can try to fill vacancies in http://pleac.sourceforge.net/pleac_erlang/index.html)

Hatena Bookmark is killer twitter? No. it's beyond.

here is just my humble opinion...

Japanese visionary, Mochio Umeda recently made controversy comment in his interview.
He said 'So sorry for Japanese-internet-scene. Now, just a underdog'. (this is not precice translation, but most of reader took it as such.)
He is a vice president or such a position in Hatena(hatena.ne.jp), so, who claimed about his statements, blamed Hatena too.

I have no spare time to blame anybody. But I have time to check the status quo.

Hatene has a lot of laboratory-level ideas. And some of thier major services are very nice and convenient, and "edge", I think.

Twitter is very simple service. Some one tweets, then others can know that.
Hatena-Bookmark(HATEBU) sevice is more complecated(maybe hard to use), but more powerful.
Hatebu user can tweet anywhere (contents) in the internet. Then, any "contents" in the internet can cite tweets as comments if they want. HATEBU API is open to contents owner. Of course, you can follow anyone, as twitter offers.
Hatebu introduces additional dimension in stream-media. If Hatena sold its armors just now, $10B would be cheap for some VCs. Hatebu may kill twitter.

In fact, its API is TOO powerful for someone who cares about bad-repuation or silly comments. But, it is easy to mask out such a noice. Just remove embeded script.

So, I'm so sorry for Hatena who does not sell their ideas at right time....