Loopt is based on Microsoft's technology stack. We use: Windows Server 2008 R2, SQL Server 2008 R2, IIS 7, C#, ASP.Net MVC 2, WCF, AppFabric and more. We als

Loopt is based on Microsoft's technology stack. We use: Windows Server 2008 R2, SQL Server 2008 R2, IIS 7, C#, ASP.Net MVC 2, WCF, AppFabric and more. We also use Ubuntu, Apache, PostGRE SQL, and many other open source technologies and libraries. I'd imagine most people don't use Microsoft's offerings because they're expensive (but affordable with volume licensing). They're also rarely on the bleeding edge, but sometimes that's a good thing. They offer some things you can't easily get with open source offerings, like: SQL Server: Mirroring, Transparent Data Encryption, Spatial, Partitioned Indexed Views, and Full Text Search (all in one offering) IIS 7: Ability to host transport independent services. That means the same code can be accessed over TCP, HTTP, MSMQ, or custom protocols you write yourself, and all be monitored and managed (lifecycle, health, etc) from one place. The closest open source offering I've heard of is Mongrel 2 (which looks awesome). And so far, I've only encountered one bug that's affected our production code. It's really quality stuff that just works.