Yes, wallet hacking is very possible and our accounts are very vulnerable to hackers. My aunt had experienced this, she sent his MEW address and private keys through the online messaging to his husband and kids just to be sure that she has extra copies, but three hours after she received her tokens from the bounties she has joined, the tokens were no longer in her account. So lesson learned after that. Dont send it to online messaging and dont click on any sites or links that are unfamiliar, these may be phishing sites.