A friend put his phone number (and possibly the IMEI) for his android device into some kind of hacking PC software that promised to (and actually did) extend his Whatsapp account that was about to expire. We all know Whatsapp uses your number as user-name and the device IMEI (reversed and md5-hashed) as password. Certainly his account was compromised: someone would have been able to steal all his account data. This is why I completely deleted his account and uninstalled the app.
Disclaimer: I've read the security.stackexchange.com question What is the risk of leaking IMEI / IMSI numbers over a network but it's related to mobile device privacy and installed applications.
Now, my concern is:
Is it now possible to "clone" his device and possibly being claimed as responsible for misuses that he clearly didn't do? According to this source, should be possible.