http://www.google.com/support/forum/p/Google+Mobile/thread?tid=64de7d408b32e021&hl=en

I've heard from several people and there is activity on Google's support forums that users submitting queries to Google SMS are getting spammed in return with dozens of text messages. Does anyone at Google have insight? When will this stop?

There is currently a bug, google is investigating.

"We're aware of a problem affecting a small subset of users. The affected users are receiving repeated SMS messages from their mobile carrier regarding Calendar events. We will provide an update by 7:45 Pacific Time detailing when we expect the problem will be resolved. Please note that this resolution time is an estimate and may change.

Thanks for your understanding and patience."

"21:12 PST: After investigating the Calendar SMS issue, the cause seems to be related to an error with the mobile aggregator used by many carriers. We've received confirmation that a fix is going out soon. Please let us know in the admin help forum if you're still having problems with multiple SMS messages. We appreciate your assistance and patience while we looked into this issue."