Value of /proc/sys/kernel/hostname

I've set computer hostname in /etc/hostname a while ago (also there are record in /etc/hosts). Everything worked fine, but recently I've noticed that value of hostname (and /proc/sys/kernel/hostname) changed (to hostname of neighbour computer), although I haven't touched anything related. Value of /etc/hostname remains correct. Which mechanism may cause such change? There are similar problem description , but it doesn't contains any solution.