Multiple domain names attached to same load balancer as alias records?
Yes, you can.
However, you need to keep the following considerations in mind, depending on what your application requires:
ELB forwards the
Host:header to the instance; it doesn't interpret it, so your web servers are responsible for reacting to theHost:header in the incoming request, and handling each site appropriately.ELB will load balance all the requests among all of the instances, regardless of which domain they are for, since it doesn't know (or care).
ELB can only serve up a single SSL certificate. If you are using SSL, you have to have exactly one cert that's valid for all of the domain names, or, you have to run the ELB listener in transparent (TCP, not HTTPS) mode and handle the SSL certs with SNI on the instances, themselves. If you can't meet this constraint, you need one ELB per SSL cert, so the original question is moot -- each ELB has its own target for use with aliases.