Posted by Wall Street Journal
By Betsy Morris and Deepa Seetharaman
Tech startups live by the rule that speed is paramount. Houseparty, creator of a hot video app, has an extra reason for urgency.
Facebook, FB -0.03% a dominant force in Silicon Valley, is stalking the company, part of the social network’s aggressive mimicking of smaller rivals. Facebook is being aided by an internal “early bird” warning system that identifies potential threats, according to people familiar with the technology.
This fall, Facebo…