Isn't this a bit parasitic? I thought hotels generally reserved a particular number of rooms in these arrangements, so if you take a room, that's one less available to someone genuinely interested in the event.

Do you really save that much though?

If I wasn't going to go to the expo, but still have to pay for the expo ticket price (to get the great hotel deal), I'm paying close to the price I would have paid without the discount.

Really? Put my credit card number and expiration in a Google Form?

This is my default technique when traveling to a city: check for free conventions that have hotel deals.