All of the money-related reasons others have talked about are valid, but there are also some legal reasons where you have to go public (such as a certain number

All of the money-related reasons others have talked about are valid, but there are also some legal reasons where you have to go public (such as a certain number of shareholders, which comes into play when companies give stock options as compensation). Facebook would still be private if they legally could have delayed any longer, I believe. You are entirely right that there are huge advantages to being private in a lot of cases.