It doesn't even really serve its intended purpose - encouraging civil behavior through reinforcement, or acting as a weight to sort by quality. And the fact that there are no guidelines for voting means that it carries very little context as well, besides being a general indicator of account age.
This is just my opinion, and I am open to hearing anyones and better understanding of the importance of Karma, especially given that I still feel that the internet is in its infancy)
Karma is a a valuable social lubricant within the context of the site, community, and topics discussed therein...
It serves as a queue as to the validity of either the information being shared, or the value fellow members of the community perceive the contribution to be.