In the age of social media, posting a photo of a marked ballot on Facebook or Twitter isn’t an election irregularity; it’s a sign of enthusiasm that could also prompt a voter’s friends and followers to head to the polls. Unfortunately, voting laws in Massachusetts haven’t quite caught up with technological advances.
It’s illegal to share a photo of your marked ballot; the ban is intended to discourage vote-buying, which could theoretically become more prevalent if would-be buyers can demand photographic proof. Secretary of State William Galvin isn’t exactly busting down doors to pursue violators of the law. But WBUR reported last week that after Boston Phoenix writer David Bernstein tweeted a photo of his own ballot, Galvin’s office contacted him to suggest that he remove it.

Comments
I disagree. It could do harm, including (illegal) firing based on how you vote, abuse of images, especially if online voting disputes arise.
I also disagree. The secret ballot is an absolute requirement in a democracy, and we've become very sloppy about it. For instance, when I feed my marked ballot into the machine, there's a poll worker sitting right there who could easily see how many people voted on a particular race.
They were too expensive to buy and transport, but I prefer those old mechanical voting machines where a curtain closed around you and you had absolute privacy.