If you're not using proxies and you're earning NP on more than just your main account there's a high chance of getting frozen purely because you're not allowed to earn NP on more than one account anyway even if they don't catch you cheating. Best to just avoid that risk altogether.
I've had several accounts that have been logged into several times from my computer, my main, my account I autobuy with, my sister, my wife, a friend....so with multiple accounts being used would they think it was more like a public computer if they got suspicious or would they freeze all accounts?