Bob,
How wierd! I noticed the same problem on my 1150GS on Friday. Definitely not a drip-drip sort of leak, just a mist of oil outside the gaiter (on the bottom) that connects the drive shaft to the hub.
SLM did a major service to the bike before our trip to Eastern Europe in August, so I called them. Les Walker (Service Manager) reckoned that it was safe to ride as long as the oil level was checked regularily until I could get it in for the seal to be replaced. Their normal experience was it is normally a slow leak caused by excess pressure in the hub, That in turn is often caused by overfilling. I checked the oil level. Guess what, Filled to the top of the thread that takes the filler plug. Les told me it should only come up to the bottom of the thread. So, overfilled - but it was one of Les's people that overfilled it...
I've taken some oil out, but it's still misting, so it's going back for replacement by SLM. I'm expecting them to make a suitable gesture. We'll see, and I'll let everyone know.
Cheers, Norman