I recently saw an example of Google Earth imagery being used in a land lease. Although there are probably other such cases, this is the first time that it has come to my attention of it being used in a legal document.
The lease gave the tenant the right to lease additional property from the landlord in the future. The landlord and the tenant decided to "describe" the additional property using Google Earth rather than a legal description because it was simpler and much less expensive. The lawyers were comfortable with its use as well, since in this agreement the property description did not require the specificity found in a legal description.
The use of satellite imagery is becoming more prevalent in the courtroom. It will be interesting to see if it becomes more common in legal documents as well. I can see a number of potential uses. However, I expect that it will take a while for lawyers to become comfortable in using the technology.