Oracle cloud “always free” tier – can they be trusted?

I initially assumed they would try and trick people into using paid services (e.g. by exceeding bandwith or storage limits), but that doesn't seem to be the case. From what I can gather, you would need to explicitly move into a paid tier.

But... Oracle have a certain reputation as I'm sure everyone here knows. Are there any users who can give me some confidence I'm not going to get hit with a massive bill for accidentally clicking some trivial button?