In the US unlimited messaging typically means just that. And thankfully so, because about a year ago my teenage brother was on my plan and managed to send/receive 16,000 texts in a single month.
16,000 is a large number, but it's not all that surprising. I find myself having multiple conversations at once via text often times, and will spurt out batches of around 100 texts at a time within the course of 5 minutes or so. Teenagers with a social life far more developed than my own will without a doubt hit those numbers multiple times a day.
I think a lot of this is because of the change in mindset of texting. Early on, it used to be a way to convey precise pieces of information. Now it's conversational. People send texts with "um" as the entire message.
