problem of the Internet   

robust scalability of routing system 
closely related to configuration management
primary factors in routing evolution:
relative cost-performance of communication, computation, and human brains
tradeoff between fast convergence and stability for current IGPs
timers limit effect of external instability at expense of increased convergence time
hard to get data to do real studies/analysis to discern real from artificially imposed instability 
better damping algorithms remain elusive
researchers & sysadmins can help optimize navigation of trends
less hope of changing them
worse news: we really don't understand the design space
routing architecture stagnates (unless you count the hacks)
no way to judge success or failure of proposed architecture
or verify operational integrity 
any change sufficiently ambitious to address problems is also sufficiently ominous 
                to scare any vested interest whose support is required
in meantime, problems with current routing have not even begun
BGP has no mechanism to route around saturated chunks of core 
core Internet chunks operate for weeks/months at/near capacity
too much manual tweaking going on to justify an assumption that hell won't break loose at some point
proposed overloading of BGP infrastructure to distribute "non-routing" information"
auto-discovery mechanisms for Layer 3 VPNs [BGPVPN] 
not particularly comforting that we're adding even more responsibility to a system we don't really understand