HN's readership wields significant influence in SV/SF tech, both collectively and individually. Check your server logs, I bet you got hits from inside Tumblr's IP block almost the instant it hit the front page, along with virtually every other tech company, whose employees and even executives were glowering at their friends (and former and future colleagues) at Tumblr.

To use the indelicate phrasing of my first manager, bay area tech is highly incestuous.