Barry Schwartz at the Search Engine Roundtable has some screenshots of Google SERP listings where some of the long URLs are truncated to be only one line.
It doesn't seem to be happening for all URLs on all SERPS, but it's definitely happening for some of them. A quick look seems to indicate that Google are more likely to truncate part of a URL path (the folder names) instead of the filenames. They always seem to keep the beginning of the filename (whether it's located in the root or in a folder/directory), but they sometimes truncate the end of the filename.
Gotta love Google with incremental changes!