Is Steam safe and suitable for a 14 year old

My daughter has moved on a bit from Flipnote and now plays Minecraft or some games on Steam.

I read about some Steam vulnerabilities on Wikipedia so are just wondering is it really suitable for a 14 year old.

She does only have it on a separate PC and only plays in the same room as us, but is there anything we should really be concerned about and keeping an eye open for?