I met this one girl and we both added each other, but it was really confusing. On my Friends List her caption would sometimes say, "Open your gates," or "What time can I come?". It was really hard to communicate like that and we never visited each others' towns regardless.
Plus, I cleaned out all my friend codes a few months ago, so she's gone now.
I've only had nice experiences so far, but on the occasion someone asks for my FC and a visit to my town, I politely decline. Only one person ever persisted, so I suggested visiting their town first. They declined and let me be.