Have there been any changes to the tank recently? Even something as simple as changing of bulbs in a T5HO or MH unit could cause such an event from minor stress. Typically, splitting isn't a good thing. It is a 'last ditch' effort to preserve itself.
Though this being said, people have reported healthy splitting of their anemone...though I have never experienced this personally...and could still be explained by the bulb situation I stated above in a tank with stable and pristine parameters.