Yup. Friend of mine had a Specialized Epic from the early/mid-90s that was carbon tubes with aluminum(?) lugs. It eventually disintegrated where the two materials met. It's very important to isolate the two materials by adding something like a layer of fiberglass between the carbon and the metal (when building a frame). I think Specialized started doing that partway through the production cycle for that bike.

I'm not sure if any of the people making carbon posts go to the trouble of adding this "passivating" layer, so it is a good idea to regularly remove and re-grease a post that is being used in an aluminum or steel frame. The problem is worse if you live near the ocean vs. inland and worse if you ride during the winter in parts of the country that use salt on the roads. This is not a problem for titanium frames as carbon and titanium are adjacent in a published galvanic series in sea water [Jones, Principles and Prevention of Corrosion].