I'm with you regarding online music - having my entire collection dangling on the end of an internet connection with no backup is not a route I ever want to go down.
The same goes for video content. Renting my films and TV programmes over the Internet every month is not an option. There have been situations where streaming services have refused to carry titles that are controversial, have presented films in the wrong aspect ratio and many titles, quite simply, are not even available. Plus, streaming services often only hold the rights to content for a set period.
Tying this into PPC Mac's, even my iBook G3 can play DVDs and a large selection of standard-def video files but Netflix would require the minimum of a Core Duo machine (using Silverlight 4) to view those same titles online: at standard-def. Why would I dispose of my DVDs and Blu-rays for that model? That's without even considering the loss of extras such as audio commentaries, isolated scores, features, deleted scenes and so on.
We're being steered towards a scenario where the consumer no longer owns a physical copy of their entertainment media and this is promoted as "progress." Many of those who applaud this will not realise the implications till it is too late.