When most people in Boston talk about the fiscal cliff, they’re talking about the deadline-driven negotiations in Washington over taxes, spending, and the federal debt. But Boston entrepreneurs and investors are obsessed with hurtling over a different cliff right now.

They worry that the feast of initial “seed” funding available to young companies over the past few years is going to lead to a major famine in 2013, as the crop of start-ups that raised their first $1 million discover that there isn’t enough follow-on money to support all of them.