Agreed about the FCC. For the $500/month short codes, were those unique or shared? Shared short codes don't work with 2-way communication (when someone replies, which business does it go to?).
Not ideal of course. Best to have geographically isolated short codes to minimize this. But it's better to be FCC compliant.
http://www.usshortcodes.com/get-a-sms-short-code/sms-short-c...
I'm a pretty risk-averse person and I can't imagine in any way the FCC cracking down on the use of long codes for legitimate two way communication with an existing customer. On the other hand, using long codes for mass marketing campaigns and you'll probably be shut down by the carriers and possibly sued, no FCC action required.