Don't ever attempt storing your private keys or phrases on the internet becasue nothing is ever safe on the said internet. Most computers or other devices on the internet are compromised and if such system be use to store these sensitive information then there will be the opportunity for the hacker getting the sensitive record for exploitation, ensure to keep these sensitive information off-line as the best practice.
Well.. I have seen a number of similar posts recently, and want to comment on it. IMO, it is not very risky to store your private key online. But that is only if you know how to store the key securely. You should store it somewhere with adequate security and with proper encryption. If the file is encrypted, then even if someone gains access to it, he won't be able to access the coin holdings.