Last week Barry Schwartz at Search Engine Roundtable trialled AdMob, the online advertising platform, where he blew $100 in half an hour, advertising an iPhone app.

I asked him whether it worked out or not…

AdMob is one of the leading lights on the mobile internet display advertising scene, and offers vast reach. It will only become bigger now that mobile internet penetration is skyrocketing.

The iPhone is the number one handset used worldwide by consumers who visit sites signed up to AdMob. iPhone requests have increased hugely in recent months, leaping from 28 million in July to 236 million in October.

AdMob’s network extends to iPhone apps, which Barry targeted to drive sales of his BlackBook dating management app.

So was it worth the money?

Not really, though as an isolated campaign we shouldn’t read too much into these figures. Nevertheless, it makes for an interesting case study.

The results: the ad was live for 30 minutes before the $100 budget ran out. During that period the ad generated an impressive 26,815 impressions, resulting in 200 leads (clicks were set at 50 cents). As such, the click-through rate was roughly 0.75%… not to be sniffed at, given that it is three times more than the average online banner ad.

Of those 200 people who clicked on the ad a maximum of 16 bought the Blackbook app. But Barry reckons he pulls in “16 or more sales” on an average day, so he didn’t really see any spike from the campaign.

What went wrong?

Well, various factors are at play – such is the way with advertising. These include creative, timing, brand recognition, placement, etc. Maybe iPhone users don’t like to download apps from their handsets while using another one? Maybe some of these clicks were made in error?

Regardless, AdMob is well positioned to reap the rewards of the mobile internet boom. It released some more stats that outline consumer preferences for internet-enabled handsets, which is different in the US and UK (62.8% of AdMob’s iPhone requests were from the US, where the iPhone is the #2 device behind the RAZR. Meanwhile 5.0% of iPhone requests came from the UK, where the iPhone is the #3 device behind the Nokia N95 and Sony Ericsson K800i).

Mobile is finally delivering the kind of user experience we’ve been promised over the years. The technology and the handsets have improved hugely. But despite the hype surrounding this sector (best demonstrated by the beyond-ridiculous forecasts issued by analysts over the years), and despite the groovier handsets, clients simply haven’t adopted mobile at any kind of scale. Next year, anybody?

We can’t yet say that mobile is a sure-fire winner in terms of cost-effective lead generation, or transactional e-commerce for that matter, but things are certainly ramping up in this area. And the opportunities for some brands in the areas of customer engagement and service are tremendous.

It’s early days but we’d love to hear about some best practices in mobile advertising. What works best when using mobile ad networks? And how can you avoid the kind of results reported by Barry Schwartz?

Our ears are open…