In the “why don’t they click off the time stamp” edition of this blog, there is a story about how some e-voting machines in Ohio produce a time stamp and you can use the time stamp to figure out when people voted.
I would note that this is much more a problem in low turnout elections, when people truly do come in slowly and are more likely vote relatively sequentially (of course, voter 1 is always voter 1). It is less likely a problem in high turnout, long ballot presidential election, when voters vote at very different speeds (we have timed voters casting ballots in the same precinct in the same election doing this task in times ranging from 2 minutes to 15 minutes). Voters would quickly get mixed up in the process.
Regardless, the fact that this feature either is not suppressed, or suppressed in the information provided to the public, is rather bizarre. I am also surprised that the people in the story were able to look at the un-aggregated vote totals. In most states, ballots are sealed and not available for examination after the election is certified. It is quite problematic that these people were given access to the ballots to the point that they could see the time stamps, if that is in fact what occurred.