Same error with Snort on Ubuntu (Oneiric)
I had the same error when trying to run a fresh install of snort.
"locate libdnet" didn't tell me anything, but thanks to your post I found a file /usr/local/lib/libdnet.1.0.1
So I created the ~~.so.~~ file, did the stuff you said to update, and now I get a different error message when trying to start snort
So thanks for helping me move forward