But with news that ambient's revenue broke the £100 million mark last year, things are clearly changing. Planners and buyers are increasingly talking of the discipline as a sector in its own right.
Indeed, Concord is predicting that the advertising industry will increase its spend on ambient formats by a further 10 per cent this year - considerably more investment than you'd expect from agencies finding cheap ways to keep the client happy.
Mediaedge:cia's managing director, James Whitmore, feels that the ambient moniker is no longer representative of the sector it claims to describe.
"The name should be 'environment media' rather than 'ambient'. It's all about connecting with the consumer at the right time rather than being a passive experience, he says.
This attitude seems to indicate a growing legitimisation of ambient as part of the media mix.
Concord's managing director, Nigel Mansell, certainly seems to think so: "Although ambient is still part stunt-based in order to generate publicity, there has been a reinvention of the medium so that it has become part of the natural media selection."
New opportunities to target consumers efficiently have driven ambient's exceptional growth aided by fragmentation elsewhere in the media industry. The suspension of Viacom Outdoor's much vaunted XTP system has been a setback but confidence in the sector remains high. Indeed evidence suggests that ambient media budgets are increasingly set up-front rather than being knocked together from a mainstream campaign's surplus funds.
"Ambient has gone beyond being a stunt and has become part of the established media scene as agencies seek to target consumers more efficiently, BJK&E's joint managing director, Tim Irwin, says.
But this success doesn't mean that ambient media is guaranteed a place on the schedule. As MindShare's head of outdoor, Catherine Bosworth, points out, it's likely to be the first to go should budgets be changed. But this is perhaps part of the growing pains for a sector that is garnering mainstream respect.
And it's not just the buyers' perceptions that are changing. Their reports show both outdoor sales points and, in particular, ambient specialists, gearing up their performance over recent years.
Several key players have emerged including MediaVehicle, which predominantly sells point of sale sites, Admedia and CPA in washrooms, T4, which sells advertising on tickets, and Mega Profile which handles giant posters such as that on Selfridge's scaffolding in 2000. But the sheer number of owners trying to peddle their, occasionally, dubious offerings can cause problems and irritations, not least because their effectiveness can be difficult to monitor.
But then accountability is a relatively minor issue and as one outdoor buyer puts it: "Ambient is more about creativity than monitoring numbers. Traditionally, it's this opportunity to be creative that has driven ambient's popularity with media planners and buyers.
"It's very easy to think of a good ambient solution to supplement a traditional campaign. The client will like it, you might generate some PR and the chances are that you might even win an award for it, Irwin says.
Ambient stunts do tend to feature prominently on award shortlists, yet while evidence of effectiveness remains hard to come by the danger of a backlash grows.
"Ambient has grown disproportionately so far and is likely to continue to grow because the industry thinks it is clever and it's relatively cheap. But awarding prizes for placing ads on the back of toilets is starting to get out of hand, one agency buyer points out.
Bitterness at the number of awards it receives is not the only obstacle that ambient has yet to overcome. There's the controversy over the use of illegal flyposters that built up after Britart's campaign won the D&AD gold pencil in 2000. Then, there's the proliferation of ambient formats which means that consistency of standards across the sector is still some way off.
"Some ambient media misses the point completely, Whitmore says. "Ambient does have a place and has to be weaved into the media process."
However, despite the difficulties, a growing majority of clients seem keen to support ambient as a means of reaching consumers at the right place and time. And while the opportunity to create new sites and formats remains, the growth of the sector seems assured.
As Mansell of Concord says: "Any opportunity to cut through the clutter is worth it."