I believe the net price wasn't that heavy, but it stung, because it broke the all-in-it-together logic that otherwise had ruled.

It was already a good result for the investor – the last-minute extras demanded weren't a part of any prior negotiated preference, they were just new things extracted in return for not vetoing a deal everyone else wanted.

The biggest lesson I've learned from various startups is that "all-in-it-together" is an awful lot like asking "How are you?" (The correct answer is "Fine!", even if your arm just got torn off, your cat died, and your spouse left you for a monkey): It's conversation, and nothing more.

In the end, everybody is unpredictable. If you don't protect your rights from the start, you'll have problems. Even (especially?) if you're BFFs, everything should be spelled out in advance, including metrics for conceptual terms such as "success", etc.