...

I'm opposed to some of the suggestions where to put source address filters, especially placing them in "non-edge" locations. E.g. requiring address filters at US border crossings is a *bad* idea, worthy of an official visit from the bad idea fairy.

What is bad about filtering facing non-customers, if loose rpf is used? I'm assuming this is what you mean by "border crossings" rather than the literal.

--------->makes sense on the edge/aggregation but if you do it further up in the network.....there maybe some cases where we have assymetric routing, where the path of uplink is never the path the same as the downlink, and infact the source network of the packet may never be present in the routing table....(it is possible, after all its a packet switched network and the routing is destination IP based) ...

Right, which is why I specifically mentioned loose rpf, vs. strict rpf. Even further up the customer chain, you'll still have a list of customer networks (assuming folks are doing the right thing by filtering customer bgp announcements) which could be used as an input to strict rpf.