(*) Why kudzu overwrite the ifcfg-ethX files?
(*) As I understand the kudzu run on each reboot in order to find new devices, so why this overwrite isn't happened after a reboot?

The scenario :
1) I configured bonding on redhar5.1 (eth0-eth1=bond0)
The ifcng-eth0 before the kudzu was :
DEVICE=eth0
ONBOOT=yes
BOOTPROTO=none
MASTER=bond0
SLAVE=yes

2) kudzu -p (just in order to check the devices)

3) All the ifcfg-eth0\1 was overwrited with default ones.
The ifcng-eth0 after the kudzu was :
# Intel Corporation 80003ES2LAN Gigabit Ethernet Controller (Copper)
DEVICE=eth0
ONBOOT=yes
BOOTPROTO=dhcp
HWADDR=00:0e:0c:c7:57:b8

Those files are saved in three different places. If you use the gui to make the changes it takes care of all three, if you do it by hand you have to change all three.