Planning, attempting to, or helping people escape (not stay) was the #1 reason for Stasi arrests.
Specifically, the most frequent Stasi arrest charges were Republikflucht ("fleeing the republic") and Fluchthelfer ("helping others flee")
Also, the Stasi ran on roughly 1 informant per 60–180 residents. Your network of friends, family, co-workers, and neighbors would have several. They officially criminalized private speech, correspondence and travel. The US surveillance system is bad, but the Stasi informant network and set of official consequences was at such a level as to cause constant fear and dread for everyone.