The push is on by some to have an end-run around the Electoral College. In addition to the various claims made on the Electoral College's behalf, we might add that it provides a decreased incentive for fraud.
In creating 51 different races (the states plus DC), the Electoral College provides a partial buffer against fraud: the most fraud can do in any one state is deliver that state's votes to the wrong candidate. While obviously that is a lamentable outcome, it does limit the extent of fraud and, moreover, makes the fraud only really valuable when the votes are hovering around the 50% mark (assuming a winner-take-all election, the most common system of apportionment in the US). Whether one candidate has 55% of the vote versus 60% of the vote doesn't affect the state's electoral result.
If, however, the Electoral College were abandoned in favor of a national referendum, suddenly there would be a big difference indeed between 55% and 60% of the vote. There would be an increased incentive for vote fraud, because fraud would, at any point, be valuable. Getting a 10,000 more votes in one state could offset being 10,000 votes behind in another.
I have a suspicion that the temptation for fraud can be bigger in those areas (whether towns, cities, or states) where one political party dominates: since that party controls all the levers of power, fraud is easier to effect and cover up. Currently, those areas have less incentive for fraud, since this fraud would be limited to the state. Removing that buffer of state boundaries would also remove one practical disincentive for fraud: fraud could provide national and not merely statewide benefits.
So the Electoral College may offer a way of isolating corruption in our voting system, helping our elections stay fairer and more transparent. There have been more close elections in US history than elections in which the winner of the popular vote did not win in the Electoral College, and, since close elections would be especially vulnerable to fraud, this would not be an inconsiderable advantage.