For those curious about the 160 character limit, texts are carried in the space left over per packet sent via voice communication. In the old carrier system, 128 characters was the maximum amount of space capable of being carried in that space without running over into the voice channel which they'd blocked off to ensure minimal voice packet loss (keep down jitter and let you sound reasonable). This wasn't exactly QoS, but, at the time, the closest thing they had.

Certain characters when represented in their numeric form took up two much space, breaching the triple or quadruple digits, so the decision was made to limit to a certain character set which was represented numerically with shorter length characters, boosting the final number to 160.

Essentially, they went form an 8-bit character set to a 7-bit set and discarded extraneously long and seldom used characters,

Texting's original purpose was to send out short messages and updates, not have long conversations, so, at least at the time, it was thought to be more than sufficient.

I know that's fairly non-technical (it takes a lot longer to go through the whole story), but the gist is there. Hope that this helps explain a good amount to folks who are curious.

This LA Times article gives a nice recount on what happened and how everything's transpired. [latimesblogs.latimes.com]

Hope that helps anyone who's curious!