The concern is that AdMob collected location data from its users without consent from the users or the Korean Communication Commission, South Korean police said.
Google's Seoul offices were raided to confirm these suspicions, though, just like in the Street View case, it's unclear what the police hopes to find since it's unlikely these offices contained any data or 'evidence' related to what the police is trying to determine.
Google has sales and exec teams in its local offices, but it rarely operates services locally. Most products are housed in common Google data centers regardless of which users they are serving.
Still, the raid indicates a growing concern over privacy with mobile devices. Location data collected by iPhone devices was a subject of hot debate these past few weeks and brought the issue into public eye. Apple is now under investigation in South Korea as well.
It's not the first time the Google offices in the country were raided, the police seized hard drives when investigating WiFi data collection with the Street View cars.
About a year ago, Google revealed that it had, unknowingly, been collecting payload data from open WiFi networks. This launched several investigations in most countries involved and some are still underway.
South Korean police determined that Google has indeed collected personal data with its Street View cars in the country, but no charges have been pressed yet. Google says it hasn't done anything illegal with its Street View service.
Several governments and agencies around the world are looking closer at Google's operations, either over monopoly or privacy concerns. Since the company dominates search and online advertising and is getting a solid foothold in the mobile space as well, the increased attention is perhaps warranted.