Never when using as debit (largely because the point of a debit is that you have punched in a PIN, which is your ID), and sometimes with my CC. I *always* thank the person asking, and think it's ludicrious that MC and VISA have no-ID rules. It protects me, as a consumer, if someone steals my card.
Re: minimums on CC. Being a small business, I totally understand the minimums, and frankly without them a lot of stores wouldn't be able to offer their customers the convenience of using a CC. I don't take CCs for just that reason--the fees are just too high, often as high as 15-20%, depending on the card and what the transaciton is classified as (restaurants usually pay a higher percentage than grocery stores, for example, and generally the bigger the business, the smaller the percentage overall). Tack on an extra person to do the paperwork and accounting for it (I am just not an accountant, and you really need one for this), and it's just not worth it for any kind of small transaction. Unf, many small businesses also couldn't survive in our credit card world if they didn't take them, so it's this catch-22.
Minimums of EBT & food stamps, however, is ridiculous. I actually just got back on a conference that covered some of this, and there's no good reason for it. They don't pay a per-transaction fee for these, and the system is automatic (in other words, they don't need an extra accountant for it). I do actually believe it's illegal, and you should definitely report it. Actually, I learned an amazing amount at that meeting about certification, etc. The system is better than it was some years ago, but still needs a major overhaul in many ways, at least in VA regarding things like certifications.
"This isn't life in the fast lane, it's life in oncomming traffic." -Terry Pratchett