Sorry for the late reply, I would say the STN-IBZ is going due to it not creating strong enough yields in the winter. It will be done on a year-on-year comparison with 2009/2010 winter, and then taking into account this years economic climate.
Remember for all airlines, especially Ryanair - the winter is not about what profit you can make, but how you can minimise loses, so the profit from the summer months is not hit too hard. In Ryanair's case the airline is going more and more seasonal as traffic is generated from two main sources, VFR and leisure. Business traffic helps sustain airlines such as easyJet and flyBE in the winter, and Ryanair dont pretend to chase after those customers. As in MOLs interview though expect a big change in the RYR business model in a few years, Ryanair has the lowest cost base now its time to adapt the business model, raise yields and increase profits. I would expect to see a lot of the nowhere - nowhere routes to slowly get phased out in the next 5 years, as more airports like BCN and MAD beg for the "ryanair effect" to regenerate declining traffic numbers at airports with major overcapacity. Ryanair are one of 2 airlines in the industry best placed to do this. Easyjet missed the opportunity at BCN, but with Stelios still ranting on about expansion I feel they have been slightly more cautious with new bases this year.