This November 4th voters will be consuming more than just "democratic duty". They will also be able to receive free coffee from Starbucks and free ice cream from Ben & Jerry's.
These promotions could have an effect on voter turnout this year and perhaps even in subsequent years. For this year, people who otherwise would not want to vote this upcoming Tuesday might do so if they want free coffee or ice cream (or they may at least lie about voting to get the free products). As per boosting future voter turnout, getting people together in a central location where they can boast about voting may help re-enforce the idea that voting is "good" and make people more likely to vote in the future.
The one thing that puzzles me about these promotions is why these companies are willing to pay such a high cost to get people to vote, especially since it appears that the outcome is already determined based on the polls. Maybe these promotions will have an effect on the few tight Congressional races. Or maybe these companies think people will buy more products at their store when they come in for their free products and this will offset the cost. Regardless of the motivation behind these promotions, they may affect turnout. It would be interesting to see after the election if these promotions had any effect on turnout near the stores that held the promotions.