Ask HN: Is There a Technical Decision That Snowballed and Crippled Your Startup?

I began thinking about how some decisions that seem innocuous or well-intended or naive or desperate eventually grow into very large problems that are resource sinks and from which recovery is difficult or not possible (i.e. fatal). I ask the community because I am curious about patterns that may exist or pitfalls that can be or have been identified (and any good stories/anecdotes!).