It's not because YC companies are in stealth, but announcing you're a part of YC...

gbelote on March 27, 2013 | parent | context | favorite | on: The Top 7 Startups From Y Combinator’s Winter ’13 ...

It's not because YC companies are in stealth, but announcing you're a part of YC is a newsworthy event, and that can be used tactically in coordination with something else. For example, launching a new product or campaign.