Over the past few years I have averaged 3 to 6 conferences a year such as Pubcon, SES, and SMX. Chicago is also home to an SES, Ad-tech, Etail, and other smaller conferences and makes afternoon trips to see friends and check out vendors a snap.
All of these conferences have one thing in common:exhibit halls where people are trying to recruit you to buy, sell, or partner with them on some level. Sometimes they are interesting and other times its just a waste of my time, but I go back as you never know what you will find there. This leads to a large number of vendors and in turn, sales people having my email and contact information.
Depending on how sophisticated the conference is, there are different ways the vendor can get your information. Most of the time its a “Can I have your card so I can show my boss I talked to people” or “Let me scan your ID and you will qualify to win prize X” or lastly the “Put your card in the bowl and you can have swag/register to win more swag” type of come ons. No matter what method they use, they all in the end are simply trying to get your name, title, email and phone if possible. Cant blame them for trying can you?