I did Bike Virginia a few summers ago, and part of one day's ride was on the C&O Towpath. It had rained hard a couple of days prior, so the path was still quite muddy in low spots. I was riding my Terry Isis road bike with skinny (23c) tires. NOT RECOMMENDED if it has rained at all recently there!!
After fishtailing all over the place and almost falling several times, I finally had to get out and walk part of the way.
I noticed all the fat-tire riders passing me and going the other way seemed to have big s***-eating grins on their faces,
or at least that's how if felt at the time... 