> People are smart enough to write down their address.

Not usually.

In this scenario, given its use for display on a user page, it may make sense.

For most other cases, this doesn't pan out. Here in the US, for example, the general public has little sense of how to properly write addresses with floor, apartment, unit, or suite numbers. Folks routinely put things in the wrong order or use the wrong symbol or abbreviation. Others make up nonsense and genuinely think what they have is correct. Developers and geeks aren't immune; I've seen forms that reflect an inadequate understanding of addresses.