Physical Laws of SaaS (add your's!)

(Please add your own Laws of SaaS in comments on this post. I'll include them in a Medium article. Bonus points for those who represent their laws as mathematical formulas.)

1. A user at free tends to remain free. A customer will inevitably churn.
   Churn(months) = strength of value proposition / (VC-funded competitors X 5 + self-funded competing products) - (confusion + bugs) - customer service

2. General Relativity: a relative is someone who generally thinks a payment for your product goes straight to you, has a very general idea of what your product does, thinks you should give him the product for free and thinks far less of what you are doing than the general public. A friend, especially one who knew you before you monetized your product, can be expected to behave generally like a relative.
   Feedback from paying customer = 10 X Feedback from person who convinced you to give him the paid product for free
   Word-of-mouth marketing from paying customer = 100 X WOM marketing from person who convinced you to give him the paid product for free

3. Special Relativity: A user's engagement with your product increases relative to how special the user perceives your speed of development.
   The speed of development of non-accelerated startups = the speed of development of accelerated startups; the multiplier is team. Founders who fail at team find the mass of insurmountable problems to be infinite.