If the WSJ is correct and their revenue is $250m, this values the company (admittedly growing like crazy) at 40x sales. Seems very rich to me.
Still seems crazy high, but seemingly not out of line with other recent tech valuation multipliers. There are some other insights in these comments that seek to better explain the valuation.
[0] http://www.wired.com/2013/10/twitter-files-for-ipo-2/ [1] http://mashable.com/2014/04/16/weibo-ipo/