Linux - martian source in /var/log/messages

If a host on a network cannot obtain a network address via DHCP, an address from 169.254.1.0 to 169.254.254.255 may be assigned pseudorandomly. So it's an interface without connection to the internet. That is what ARIN is telling you. If someone tries to send something to this address, it is called a martian packet.

What is plugged into usb0?

You don't tell us what the IP address of USB0 is but I guess it's not in the link local subnet so packets arriving at usb0 from link local will be 'martian'. This is a widely quoted explantion

These are packets that Linux does not expect from the direction they came from (i.e. packets from internal hosts coming in on the external interface). The cause is probably a misconfigured machine on your LAN. You can turn off logging those packets via /proc/sys/net/ipv4/conf/interface/log_martians which is documented in /usr/src/linux/Documentation/proc.txt

Wikipedia: http://en.wikipedia.org/wiki/APIPA

You can turn off martian logging if you want:

echo 0 > /proc/sys/net/ipv4/conf/{all,default}/log_martians