Google Maps is a trusted source for location information including directions, traffic and satellite imagery. The relatively high resolution images have even been used to spur new archeological research efforts, according the National Geographic. However, the satellite images aren't all the same age, with some being years older than others.
Both Google Earth and Google Maps share the same database of satellite imagery. Google has contracted with both government and private satellite owners to receive images so that every part of the world can be mapped at some level of detail. Google uses higher resolution images for more interesting locations and more heavily populated places. Rural areas tend to have less detail available in the imagery. At the best the resolution is about two feet of actual distance per pixel on the image, at the worst each pixel can represent as much as 15 feet of space on the ground.
Google typically sources the images for Earth and Maps between one and three years out, so you may be seeing images from up to three years ago in Google Maps. However when special circumstances dictate, Google will release very recent images, like after the March 2011 earthquake that rocked northern Japan. Google showed a special comparison of the older image to the devastation after the quake and subsequent tsunami to aid rescue workers in the area.
In addition to archaeology and rescue work, Google Map images can be used in finding direction and navigating to a location so you can see real images of your surroundings rather than a drawn map. Satellite information shows the effects of humanity on the world through cities, farms and roads. Google has made available the topography of the ocean floor and the mountains of the word allowing anyone with an Internet connection to virtually explore the entire globe.
Google allows the use of Maps and Earth satellite images for non-commercial, non-violent, non-invasive purposes only. Google will obscure sensitive or private information and will not allow the commercial use of their images. Some secure places such as areas of Washington D.C. or The Hague in The Netherlands are security concerns. Google will also limit or blur the imagery of people found in Google Maps images, including in the Street View feature.