Social media isn't anything new, and nor is its role in politics. As far back as 2008 Obama's White House victory was held up as the Facebook election, while current Republican candidate Donald Trump has heavily relied on his following to garner support.
In the UK, the Conservatives spent over £1.2m in the buildup to last year's General Election on Facebook, while Labour spent just under £16,500, according to the Electoral Commission. Meanwhile, the Tories spent over £312,000 on Google advertising, compared to Labour's £372.
That may have helped Cameron get over the line last year, given law restricts parties from buying TV and radio advertisement by law.
Paul Stephenson, communications director of the campaign group Vote Leave, told the New Scientist that Facebook is the prime social media platform. "There’s a massive bias towards Facebook; we think Twitter is more of an echo chamber for Westminster and journalists," he says. "Both campaigns have £7m to spend and we’ll be putting a significant chunk of that in Facebook."
Indeed, Dr Simon Usherwood, a fellow at Britain in a Changing Europe, says it's useful for both sides to use social media given that it's a one-man-one-vote. But "the way both sides are mainly using it is to convince people who already support them to go out and vote rather than to change people's minds. It's about showing that [the vote] is something you need to get motivated about".
That's probably wise of the campaigns, given concerns about how a low turnout could affect the result. Remain are particularly fearful as their supporters are thought to be more complacent about a result, while Leave supporters tend to be more passionate. Put another way, if you hate the EU, you're probably going to cast a vote.
In terms of paid-for ads, Usherwood says a lot have been placed on non-referendum websites including Facebook. "Both sides have put money behind it, it's a clear way of getting a profile," Usherwood added.
"A lot of people are not interested in the EU referendum, so online advertising on platforms such as Facebook is a relatively efficient way of hitting key demographics."
It's also of note that campaign groups (like political parties at a General Election) can only get broadcast news with their referendum broadcast, as they are prohibited from broadcast advertising.
This means "online space is a great place to sell your message with much less restriction to a much more defined audience. When advertising online you can target certain demographics, so the logic of it makes sense".
But lest we forget Twitter. Dr Clare Llewellyn is conducting detailed research on social media sentiment in the EU referendum. She says that both campaigns have been using the platform heavily, but Remain is still playing catch-up.
"There has been strong campaigns from both sides to present, with strong and persuasive arguments, as well as images and hashtags," she said.
Llewellyn says it's difficult to tell how important Twitter will be until the vote comes in, but Leave were initially stronger as they had the "machinery" there from the outset in the form of people who had already largely been tweeting about Brexit (think Nigel Farage).
And, it could all change. She says in the Scottish referendum you didn't see the side that backed the status quo (i.e. staying in the UK) acting on social until right at the end.
So, as with the vote itself, Llewellyn adds "it'll be interesting to see the how the next few weeks turn out".