Bad for clients:
Fatal for hidden services?
Anecdotally, many hidden services have experienced sustained and intense DoS attacks this year. On clearnet, these attacks may result in economic or reputation loss. On Tor, they should be treated first as attacks on anonymity. Timely blog article on what can happen if DoS attacks aren’t addressed.
http://www.hackerfactor.com/blog/index.php?/archives/779-Behind-the-Tor-Attacks.html
These attacks are so prevalent, that I have little doubt that every hidden service experiencing them has already been uncloaked and identified by someone.
(Krawetz is Computer Science PhD. Runs FotoForensics & archive.org onion service)