Most users will not be exposed to SNMP (nor will they ever find port 161 open) unless some piece of their networking equipment has an active and open SNMP service port. If our port analysis ever shows that a router (for example) or other network device exposed to the Internet has its SNMP interface open you will want to arrange to disable and close that port immediately. Malicious hackers know that some consumer networking equipment has been shipped with exposed SNMP ports and with default access passwords. Therefore, it would not be at all unlikely that such a router or other equipment would be quickly discovered and exploited. Malicious hackers would find this amusing, but you would probably not.
Not sure if that helps but apparently port 161 is used to speed up gaming but it was later proved to not to at all, according to this:
On the BT user forum, BT initially said that these ports were left open to speed up gaming. When it was proved by those in the know that this was horse manure they changed tack. They then claimed it was for network management reasons but have refused to expand on this. As a result they have a lot (more) angry users. Personally I think its a waste of energy persuing that avenue, but I'm still curious about others opinions concerning the security implications of leaving these ports open
Again, not sure if this helps at all, but this is all i found.