In a positive analysis (should rather than shouldn't), assuming no default choice, it seems rational to use Tokyo Cabinet or CDB _hashmaps_ for unordered data, and LevelDB for ordered data, from a datastructure and performance standpoint.
It's as rational as doing optimizations. If the specific performance is extremely critical, yes, it definitely makes sense. But LevelDB does well with random reads [1]. With all its features and its permissive license, I think it's a strong contender as developer's go-to embedded key-value db, like SQLite for relational data.
Don't get me wrong, I do think your comparison is valuable, but I'm afraid it could be misleading; I specially found the wording LevelDB is for if you need ordered data misleading. Someone could read it and assume that LevelDB doesn't do well with unordered data.
[1] Compare today's benchmarks with these http://fallabs.com/tokyocabinet/benchmark.pdf, it looks like random reads in LevelDB are quite faster than BDB.