The level of investment in mobile media was raised another notch last week, when Nokia bought mobile advertising firm Enpocket in a deal understood to be worth £75m.
Nokia's move into mobile content and advertising is just one of a series of events that have raised the hype around mobile media yet again. But now it appears there is a huge amount of money behind it.
Industry executives have said in the past that mobile would only become mainstream when companies such as DoubleClick entered the space - and now it has.
Not only that, but Google has invested hugely in mobile, launching a new and improved mobile search engine last year, and last week rolling out AdSense for Mobile, enabling publishers to run on-site ads relevant to their content.
Meanwhile, companies from WPP to Aegis to Nokia have all spent millions buying into the emerging medium.
Jon Carney is managing director of Marvellous Mobile, which was bought by Aegis for a rumoured £10m in June this year - another sign, he believes, of the medium's growing importance.
"I forget where we are in the hype cycle," says Carney. "But for us, we genuinely believe that we're at a tipping point.
"There are now lots of great opportunities that weren't there before, and there is decent content for people to interact with. Click-through rates are very high, money is moving into mobile and mobile media is definitely coming of age."
A few years ago, people may not have believed that the nation's biggest selling daily newspaper would include mobile in its strapline.
The Sun's "paper, online, mobile" branding exercise is part of owner News Group Newspapers' huge investment in mobile. The latest deal has seen The Sun join up with Sky to deliver Premier League goals to mobiles for 50p each, or £5 for a month's subscription.
Mike Gordon, deputy managing director of NGN, remains unconvinced, however, that mobile is at a tipping point.
"There is a tremendous amount of energy and enthusiasm for mobile advertising at the moment, but it's not right to say that mobile is at a tipping point," he says. "We've had a very clear strategy for more than a year that we'll push three platforms: paper, online and mobile.
"Mobile is a long-term strategic distribution platform for us, and the thing about mobile is that it's a radically different platform from anything else around.
"You've got five major network operators as gateways and media owners going direct to consumer, so it's more complex than most."
NGN has started trialling video advertising on content hosted by mobile network 3.
Gordon sees this as a route with major potential, but for media owners to embrace video and banner ads on a large scale on mobile, they need companies that can provide the required ad serving technology and reliable tracking.
That's where companies such as Google and DoubleClick come in. Google is currently in the process of taking over DoubleClick, but both companies have been ramping up their mobile focus in their separate ways in recent months.
DoubleClick Mobile launched this week (page 13), bringing one of the world's biggest internet ad-serving firms to mobile.
Ari Paparo, vice-president of rich media and emerging technology at DoubleClick, says: "Media firms are starting to develop the ability to sell across mobile and we can provide the reliability of reporting and tracking to the medium.
"Accuracy has so far been a problem in mobile reporting, as no one else has invested in it."
One barrier Paparo sees in the development of mobile media, however, is the difficulty in tracking video ads on mobile.
The Sun has started trialling video ads with its content on 3's portal, but Paparo sees difficulties in calling them to account.
He says: "It's closer to linear TV than online advertising, in that it's difficult to put smart technology into it to get accurate reporting."
Last week saw the latest mobile investment from Google, when it launched AdSense for Mobile, part of a series of mobile products being rolled out by the search giant.
David Zucker, group product director at Google, says: "Every year you hear that it's going to be the tipping point for mobile, but it's a more gradual process than that. Companies are certainly moving in the right direction. They're creating more things for users to do on mobile and we're seeing stronger and stronger adoption."
The commitment of these companies, along with Nokia and the launch of the iPhone and a Google phone, will make it easier for publishers to make money and bring mobile into the mainstream.
As Tom Henriksson, director of Nokia Ad Service, says: "Many companies are looking at mobile advertising at the moment, proving our hypothesis that now is the right time to invest."
MOBILE'S TIPPING POINT?
17 September: Nokia moves into the advertising market by buying mobile advertising agency Enpocket, in a deal understood to be worth $150m (£74m)
17 September: Google launches AdSense for Mobile, enabling mobile publishers to make money out of traffic by running contextual ads on their mobile properties
18 September: Apple announces an exclusive deal to partner with O2 for the UK launch of the iPhone on November 9
25 September: DoubleClick launches DoubleClick Mobile, making it easier for advertisers and agencies to initiate and manage mobile advertising campaigns.