Interesting stuff, folks.
I lived on Martha's Vineyard for about seven years, and during that time Clinton visited regularly. I can tell you that at that time (pre-911, remember), the "disturbance" to public places basically traveled in a large circle around the man (or Mrs. Clinton)...So if he was staying at his condo, you wouldn't know unless you went out that way. And when he came into town, the area immediately around him was upset but you could be a few streets over and never know.
Still, I have to echo some of the comments from those experienced w/ the Bush compound in Maine. A lot depends on where the POTUS is, and whether it can be easily protected - or, "cut off", to put it another way.
BTW, I thought some of you may be interested in the Oct. 30 post on this Lakes Region blog about Romney and his relationship w/ the Town of Wolfeboro...
http://lakesregionofnewhampshire.blogspot.com/