[vacri]

I could see someone go through the 100 SMS very quickly in a "conversation" where the imaginary person has to answer a bunch of short texts like "yes", "and you"

It's not meant to be a discussion service, but fake evidence that you've got a significant other.

[Raphmedia]

Yes, of course. But the best way to fake evidence that you have a significant other is to build a SMS history. I send my (real) girlfriend 15 to 50 messages a day. I don't think I would fool anyone with an history of 100 messages a month.