BGP peering via default route

[Kashish_Patel]

I read http://blog.ipexpert.com/2010/11/08/bgp-peering-and-default-routes/ and understood that BGP speaker will not initiate BGP connection with the other BGP router if it can reach it via default route only...And BGP peering will not come up at all if both the BGP speakers know each other via default routes only....I could not understand the reason behind this though...Could any expert help me in understanding the underlying reasoning?

[Seth Bjorn]

I can't think of a reason why you would want to peer with a router you don't have a route for. If you're relying on a default route for a multi-hop bgp peer session, it could cause the session to be unreliable due to changes in the network down the line from you. An unreliable bgp session would be bad on the router's cpu/memory if the session were to flap.