This can only be a fair alternative if a single search can transparently query all instances (an implicit requirement for most users), and there's also an easy,

This can only be a fair alternative if a single search can transparently query all instances (an implicit requirement for most users), and there's also an easy, instance-transparent, preferably free way to upload content (requirement for most creators). Once one has the question "which instance should I search/create my account on?", it will be considered a failure.