a hash with all the ip/mac couples to be found on the local segment ... mac/ip couple is selected ... ARP replies are sent
If the switch learns from the faux replies, it may begin to forward you the traffic intended for that address. In effect, you're DoS'ing the innocent bystander.
Other hosts on the network are your peers. One needs administrative control (of the networking equipment) to choke ports or enforce policies. Also, as far as layer 2 protocol is concerned, the "attacker" here is a well-behaving host.
I encourage everyone to contemplate on the philosophy of the well-known Part 15 of FCC rules:
1) This device may not cause harmful interference.
2) This device must accept any interference received, including interference that may cause undesired operation.