At the moment, bitcoin does not verify that the outscripts of transactions are syntactically valid. Thus it is possible to create a transaction with junk in it's outscripts and get it into the block chain. No one could spend such coins (at least until the opcodes change). The question is, should such garbage transactions simply be rejected out of hand instead?

I believe the main blockchain has no such garbage outscripts in it yet, so this change could be effected now without harming the chain.