The effect of an unreliable or malicious leader is fewer transactions than possible or unfair prioritization of transactions, but limited to a single (10 minute) block. Seems like if it were an uncommon event it should be not-very-consequential.
Then again, if the lottery likelihood is a function of hashing power then maybe it's not so well distributed.
Then again, if the lottery likelihood is a function of hashing power then maybe it's not so well distributed.