Dropbox Inc has secured $250 million from Blackrock Inc and other investors in a new funding round that values the provider of online storage services at almost $10 billion, the Wall Street Journal cited unidentified sources as saying. Dropbox, the six-year-old Silicon Valley startup many expect to go public sometime this year, is taking advantage of flush investors and skyrocketing valuations for fledgling tech companies. Dropboxs other investors include Goldman Sachs, Sequoia Capital, Accel Partners and Index Ventures.