It has been proposed recently \cite{son} that excitations in Spin Ice can be of the form of magnetic monopoles that does not obey the Dirac Quantization Condition. It is also well known \cite{rj} that the above scenario leads to non-associativity among translation generators. It will be interesting to see how the monopole picture in Spin Ice survives in the light of the latter observation.
Cite
@article{arxiv.0801.3134,
title = {Comment on Magnetic Monopole Excitations in Spin Ice},
author = {Subir Ghosh},
journal= {arXiv preprint arXiv:0801.3134},
year = {2008}
}