Here's an interesting Google Earth blog post. It is the best explanation I have read of why satellite imagery from any service is so often out of date. I noticed recently that some of the free imagery available in Depiction's quick start data is over 10 years old (Stanwood, WA, USA). This post may not explain that, but keep in mind that Terraserver (the imagery I refer to) is free, and much of what the GE blog refers to is very expensive data (available only to the likes of Google and Microsoft).

Happy Depicting!
George