I like the Paul Graham notion that indicates a startup has failed. Once you refuse a phone call from PG or he doesn't hear back from you the startups finished.
This assumes that PG is calling you- not exactly a generalized model.
I think the sentiment from PG is that when the line goes dead, it just shows the founder has given up. It is an important flag for any mentor/investor to see that the founders have lost their commitment, but it doesn't say much about the health of the business itself.
This notion from PG doesn't consider the case when the founders are beating a dead horse (not making sales, refusing to pivot, etc.) yet they are adamant about continuing work as usual. This situation is more likely to occur when the company lacks a good support network, or merely lacks the ability to hear advice.
I think the sentiment from PG is that when the line goes dead, it just shows the founder has given up. It is an important flag for any mentor/investor to see that the founders have lost their commitment, but it doesn't say much about the health of the business itself.
This notion from PG doesn't consider the case when the founders are beating a dead horse (not making sales, refusing to pivot, etc.) yet they are adamant about continuing work as usual. This situation is more likely to occur when the company lacks a good support network, or merely lacks the ability to hear advice.