Ask HN: What is the stupidest startup idea you ever had/heard?

They sounded stupid^W bound to fail at first, especially before seeing the implementation / impact:

Better search engine with no sponsored listings, seamless sync and backups, short status updates blasted to your followers, better social network, animated movies that target adults, online book store (without a book store experience), $4 lattes ...

Some ideas that sounded awesome and turned out to be awesome:

Open source and breakfast bars.

To be fair, many considered open source to be blindingly stupid -- "Anyone can edit the source? That would be madness! And why would anyone just contribute hours and hours of their time? Why do you think Microsoft pays their programmers so much."

But then, "They laughed at Columbus, they laughed at Fulton, they laughed at the Wright brothers. But they also laughed at Bozo the Clown. -Carl Sagan"

for

Say you want to gift someone but you don't know what they want / don't want to buy more stuff / etc. So you buy a card that has a message ("Happy Birthday!" or whatever) and a number of credits associated with it and you give it to someone. The person, then, can use the credits to give things to non-profits, like a shirt for the homeless, or some food for a orphanage.