You probably have known that Pidgin is now able to send text messages to cell phones using a global carrier. I have posted this before on this blog, but what i haven't mentioned on that post is the limitation for this service (since i am not aware of such things at that moment).
It seems that sender have a limitation around 5 text messages for a same number. Can you send more? Yes, you can, but the receiver must reply one of your text message and using the global carrier (which probably means international rate will be charged) and not replying to your cell phone number directly. This only applies to same number, so you can get another 5 messages to different number.
I hope this clarifies the SMS feature on Pidgin.