In general, if you are going to use computers to plan actions then the action is as 'secret' as if someone was carrying a mobile phone, although that is fine is the action has been well advertised. It does look fun for initial planning. It would've saved me the humiliation once of having to stop a convoy of activists on a 'surprise' action at Menwith Hill to ask the cop car trailing us for directions to the base (and then the dilemma whether to believe them). It shows Faslane but not the subs, the water is either hidden or "We are sorry, but we don't have any imagery at this zoom level for this region".

Even if you trust google acting ethically, then you shouldn't trust your ISP. A sudden surge of activists all looking at one location could be noticed.

Google's dilemma: privacy vs. police
 http://www.csmonitor.com/2006/0126/p01s02-wogi.html

"I don't know if a lot of companies are in the business of civil disobedience," says Bruce Bernstein, president of the New York Software Industry Association. "In most cases, they would ask counsel, and in most cases, the lawyers would tell them to follow the path of least resistance. And they'll comply."

Google and your ISP might know tat you are using google maps but they are not going to know WHY you are using google maps. There's no reason to worry about planning with this application.

It's down to your definition of acceptable risk. If you are planning an action against a remote military base security or surveillance could be increased if they see a flux of activity from the usual suspects. I'm surprised google haven't linked it to their 'adwords' so that whenever you look at a military base it displays adverts for bolt-cutters, spray-paint and such as an overlay.

I wouldn't be too sure what information can be gleamed from website traffic analysis, data-mining techniques do throw up counter-intuitive non-causual relationships. Unshaven men die of heart-disease, that sort of thing. There was a similar argument over whether to use multimap or other pre-google map sites. I don't know if they do this ( if they don't it won't be for moral or legal or technological reasons ) but I bet if I had access to police records and to every ISP and phone company then I could predict when actions were going to take place. Most people give away more about themselves than they realise. Perhaps they have human intelligence that certain people are going to hit somewhere, and they find only one common map of a possible target on each of their computer records.
Like I say, if its advertised action and people are carrying mobile phones, then don't sweat it. However if you are facing serious time or have a really vital action then being paranoid and encouraging everyone else to be paranoid is a sensible state of mind and pays dividends. Even if it's just a wee action there is nothing more deflating than getting the almost coital buzz of adrenalin that you get as an action starts interrupted by a van load of polis.

All code released in the US goes to the NSA as part of its approval process for government contracts. The NSA wrote the definitive standards for securing Microsoft operating systems. If you know all this then you're perfectly able to decide what level of risk you are happy with. I at first thought activists were being paranoid taking the batteries out their phones, now I wouldn't be happy with a dead phone within fifty feet of planning.

...