It also made for some uneasy bedfellows, with one Labour candidate, Toby Perkins, using a widely tweeted picture and quote from Margaret Thatcher to register his opposition to personal attacks.
Mr Miliband said the defence secretary had demeaned himself and his office. But Prime Minister David Cameron said Mr Fallon was "absolutely right".
A glance through the social media accounts of established political party names and official accounts also reveals a good deal of negative campaigning.
Boris Johnson, Mayor of London and Conservative candidate for Uxbridge and South Ruislip, has been leading some of the Conservative attacks via social media, with tweets such as this one:
John Prescott, Labour's former deputy prime minister and prolific tweeter, has also been targeting candidates from his party's opponents.
The Liberal Democrats have also been tweeting their own targeted videos.
With weeks to go in one of the tightest polls in living memory, there may yet be further negative campaigning, but whether it gets quite as personal as previous campaigns - such as these examples below - remains to be seen.
In 2001, Labour was seeking a second term under Tony Blair. It targeted the Conservative leader William Hague by planting Baroness Thatcher's hairstyle on his head, in one of the most notorious campaign posters in living memory. Labour went on to win re-election by a landslide.
Creative photoshopping had already been used by its opponents in 1996, when the Conservatives unveiled this "demon eyes" poster of Tony Blair a year ahead of the 1997 election, which saw Labour sweep to power.
Compiled by Stephen Fottrell.

Saints finished fourth and Warrington's victory at Hull means they will face the League Leaders' Shield winners away from home in their play-off semi-final.
Tries from Louie McCarthy-Scarsbrook and Jack Owens put Saints 12-6 up at the break, with Craig Hall responding.
McDonnell's treble after the break helped to seal the win.
Theo Fages added the hosts' sixth try to complete the victory, while Wakefield - who suffered a ninth successive defeat and finished bottom of the table at the end of the Super 8s - managed only a Tom Johnstone score in reply after the break.
Victory extends St Helens' winning run to four matches leading up to the play-offs, with their only defeat in their past 12 games coming at Warrington in August.
They now travel to face the Wolves at the Halliwell Jones Stadium on Thursday, 29 September, looking to return to the Super League Grand Final for the eighth time in 11 seasons.
St Helens assistant coach Sean Long: "Shannon had a great game and went really well against Widnes last week. He's given us a headache for next week.
"Full credit to Wakefield who had a real dig at us. We were a little bit off and it wasn't a great spectacle, but we would have taken 32-12 before the game.
"The main thing is we came through unscathed for next week."
Wakefield head coach Chris Chester: "We played some really good football at times. We wanted to throw the ball around and enjoy ourselves and there was a lot of spirit and pride.
"We probably tried too hard in the second half but the final scoreline didn't reflect our effort.
"We have got into the top eight through hard work and we now have to continue with our progression."
St Helens: Lomax; McDonnell, Percival, Peyroux, Owens; Turner, Walsh; Vea, Knowles, Amor, McCarthy-Scarsbrook, Greenwood, Thompson.
Replacements: Walmsley, Wilkin, Fages, Davies.
Wakefield: Jowitt; Johnstone, Lyne, Arundel, B Tupou; Hall, Finn; Simon, Sio, Fifita, Molloy, Ashurst, Harrison.
Replacements: A Tupou, Arona, Crowther, Yates.
Referee: Joe Cobb
Thursday was seen as the day the 2015 UK general election campaign turned negative, with many reacting on social media to Defence Secretary Michael Fallon's attack on Labour leader Ed Miliband.
[NEXT_CONCEPT]
Shannon McDonnell's hat-trick helped St Helens round off the regular Super League season with a routine home win over Wakefield at Langtree Park.