My credit-card company has developed a new scheme for trying to trick me with speech-acts. It's likely that you've heard roughly this pitch before, especially if you are lucky enough to work at home sometimes and trusting enough to answer the phone before ring #3.
The scheme works like this: After lots of polite forms and attempts at charm, the telemarketer says something like, "I just need you to confirm your address for me so that I can send you a free gift certificate in the mail and enroll you in special program P. Special program P has many virtues [... tedious list of supicious-sounding virtues elided ...]. Can I get you to confirm your address for me, Mr Potts?"
This is designed to be distracting. You think, "Could my credit-card company have my address wrong? If so, the consequences could be dire. Missed bills. Identify theft. What's more, I can eliminate the risk by just checking quickly with this person. So I might as well verify this information …"
At this point, costly program P is likely to have drifted from your thoughts.
That is the insidious part. The situation comes to this: The speech-act of confirming your mailing address (just a well-placed, "Yes, that's right") enrolls you in a costly program. (Free for the first month. Always costly after that, and hard to notice on your bill.)
This is well outside normal linguistic experience. It would be no surprise if saying, "Yes, I want to enroll in P" constituted the act of enrolling in P. That is the sort of thing we do all the time on the phone — when setting up electric service, subscribing to magazines, and so forth — so we're used to it. My credit-card company's pitch avoids this direct interaction. Instead, it quietly establishes an unexpected connection between verifying some important information and agreeing to enroll in a costly program. The set-up is not particularly clever. It works only by playing on people's fears about what would happen if their credit-card company had an incorrect address for them.
So, when the telemarketers call, be careful what you acknowledge to be true. It might not be the speech-act you thought it was.