I don't think it's selling anyone on the spot but it is passively creating social proof.

I suspect street marketing is a good touch point, speaks to grass roots and down-to-earth, but also by nature of being a sticker on the street it also is not in a format that others would take seriously either.

There is not bad publicity

Bitcoin is a complex idea. Thus, it is more important that it's spread over strong channels like personal relationships, or at least some that contain trust. Those are the way for complex ideas to be conveyed and reinforced

We are better with it than without it.

Its all publicity & attention

Guerrilla marketing is cool, you see...

Lucky you. In my town I only see commie stickers. Like "Believe in communism? Join our march to fight for our cause!" etc. They haven't managed to convert me, so the Bitcoin stickers may not convert fiat believers either, but i don't know if the analogy holds.

A positive mention in the MSM would be impactful on the normies while a random sticker might impact teens more. I think MSM would have bigger impact in absolute terms but teens will appreciate Bitcoin on a deeper level.

I say effective because it costs so little. Just saw a 0.2 BTC painting with a Bitcoin sticker as part of it. So I guess it's a quality logo that can go anywhere.