What is currently the biggest thing in social media, to which you should really be paying attention? It is always a tough question to answer, even more so this week, in the wake of the US election campaign, in which social media and digital played such a central role.
Was it a decisive factor, though, and was this 'the Twitter election' at which we looked in depth in last week's issue of Marketing?
We could debate that one for a long time, for the life of the next Presidency even, but one thing is not debatable. Every now and again, a game-changing event comes along that makes you sit up and take notice.
Last year it was the Arab Spring and the death of Osama bin Laden, and how those events unfolded on Twitter.
This past week, it has been Superstorm Sandy, and how photo-sharing app Instagram's big citizen-journalism moment emerged not from the dusty streets of Arab cities, but the storm-lashed sidewalks of New York City.
Instagram was big before Sandy blew across the Caribbean and swept up toward the Eastern seaboard of the US. The app already had 100m members, having grown hugely since Facebook snapped it up for $1bn (£620m) in the spring - a figure that no longer seems so jaw-dropping.
Since Mark Zuckerberg pounced on it, Instagram has added more than 70m users, with its growth powered in part by its arrival on Android. Once it had launched its Android app in April, its user numbers quickly jumped by 10m, to 40m.
Many people who hadn't spent much time taking photos before began trying it out. It seems no exaggeration to say that something akin to rocket fuel has propelled that growth further as Instagram's users document the Superstorm.
The death of bin Laden was described as Twitter's 'CNN moment'; the arrival of Superstorm Sandy has been Instagram's equivalent. It has become the lens through which many of us have viewed the devastation. The numbers are impressive; in the first few days of the Superstorm alone, about 500,000 images were shared.
Instagram chief executive Kevin Systrom said that there were as many as 10 pictures being posted per second. We are already familiar with the Twitter language that has evolved to tell us how big an event is in terms of social media. During the Presidential election, records were broken for the number of tweets per minute, or TPMs; now it seems likely we will be talking of Instagrams per second or minute.
Before we get entirely carried away, however, it must be said that none of this would be possible without a lot of assistance from Twitter or Facebook. They are the platforms through which many of us have been viewing these images.
The elevation of Instagram this past week speaks to the lofty ambitions that Systrom has for this social network. He said recently that he doesn't want it to be a place simply for people to share images of their purchases, but one where serious news and meaningful glimpses into the lives of others are shared. Nor does he want it just to be about 'pretty filters and pretty photos', but rather 'more exploration and communication'.
That suggests growth potential, scope for experimentation, and opportunities for brands. Some have already used it with great success. There have been campaigns from bmibaby, shoe brand Aldo, Ford and Sony, among others.
Brands, then, should be looking ever-closer at Instagram, as it swells in size and significance and becomes a more essential part of the social-media landscape.
Gordon MacMillan is social-media editor at the Brand Republic Group and editor of The Wall blog @thewalluk. Follow him on Twitter: @gordonmacmillan.