Also got tagged for a $9.99 monthly recurring charge, described on my bill as "PREM_SMS 23687 23687 solow.com." Like austingrrl, I vaguely remember taking some silly survey on Facebook which resulted in getting a couple of SMS texts. I thought nothing of it, since nothing in the language indicated I was subscribing to any sort of service. I only found out when I scanned my bill more closely. I suspect like many people, I have a rather large monthly bill covering many handsets and a datacard, so a $10 difference doesn't necessarily stand out.
The lesson: Be careful when you connect the web to your SMS inbox in any way--you never know what you might be signing up for, even inadvertently.