>> My personal opinion is that javadocs should introduce compile time dependency...

Incidentally, we just had an interesting case where a library X had a javadoc comment referencing a outdated and no longer available class of library Y. Library X still had the outdated version in the compile classpath. The IDE added the import for that (no longer existent) class. This ended up in library X blowing up at runtime where the newer version of library Y was present (one which didn't have that referenced class).

Long story short, IMO, a hard dependency isn't desirable for classes used in javadoc. Of course, we would have broken javadocs in cases like the above one, but at least it won't render the library non-functional due to this specific issue.