I'm level 23 and an elder dragon just decided to make his acquaintance as I was hiking from one city to another. This did not go well for me.
Now I've experience more sudden, odd spikes in difficulty (a memorable one was a bandit marauder at the end of a cave filled with regular bandits and thugs when I was level 16).
Are the occasional enemy spawns that are way, way higher in level then you normal and has Bethesda coded Skyrim to randomly go “Hey player, screw you!”, or did the level scaling system blew a fuse or two here?