Aluminum House Wiring

Why is aluminum wiring of concern? Is it likely to return with increasing copper prices?
1. Problems: Aluminum expands and contracts with temperature - much more than copper. This means that wherever a wire is connected by a screw (most connections)it will eventually loosen. This leads to a bad electrical connection, overheating, arching, and a high chance of a fire.
 
This is particularly a problem with older houses wired when aluminum wiring first came out and they used new wire with old connection termination technology.  The new wire used with compatable connection technology is supposed to be as good as copper.  See Aluminum House Wiring for more info.  Here is another semitechnical read - Hansen.