On the search side, there's nothing stopping a carrier from indexing public SMSs and making them discoverable. We're not talking about rocket science, in the basic realization [0].
I'm not sure why HN is looking at these things like (short blobs of text) are completely different than (short blobs of text). Everything built around them is plumbing. Complicated, difficult plumbing, but plumbing nonetheless.
I'm all ears as to why providing an SMS service that supports all of Twitter's features would have been technically impossible... say, circa-2000.