The bomb-shelter mentality among startups is now so severe that even companies raising money are announcing layoffs in response to diminished economic prospects.Boston-based Helium just closed a $17 million series A financing about ten days ago, and then cut 30 percent of the organization (18 people) last week.CEO Mark Ranalli tells me: We expect a deterioration of overall ad rates, and a slowing of the economy in general.Our approach was to take a third of every group across engineering, custom