Any online game naturally relies on its servers, and when the game goes down it can be a frustrating experience. During beta testing, one of the key goals for SI will, I guess, be seeing how the servers cope with stress and load, and what makes them fall over.
The servers have been remarkably stable, but they have gone down today for cluster 2 - no Gameworlds 4,5 or 7. People might have to ring their Mums instead... Anyway, SI are on the case, and will get it sorted soon I'm sure.