when your friends have a "great idea" for an app and expects you to code it all and they forget about it after you code it...

Shhhh... that just means they have no claim to the intellectual property! Keep your head down, move to Silicon Valley, be the subject of a biopic called "The Social Network", drown in cash.

Next episode of Game of Thrones, the drowned in cash men: "What is pivoted may never die"

When friends ask you to code an app and expect you to make databases choices with no idea their expected growth, requirements or data structures.

"Can't you just pick a database, that's hard tech stuff?"

"Not without knowing your needs. If I pick the wrong database it might fail to scale and you blame me, no thanks!"