IMO BlackCoin could be serious threat to DarkCoin. As a community we should take it seriously:
1. If BC implement DarkSend, DRK could be doomed
2. BC multipool is going to use X11 (this is already happening, it is just a matter of days)
3. I think that more "average Joe" kind of people will consider DarkCoin just a copy of BC because they will firstly hear about blackcoin, which is a big hype nowdays, and they have great marketing(Apple is big copy-cat, but people find it innovative ).
Pumps (and dumps) happen in altcoin-land all the time. Stop panicking. And if BC tried to mine DRK, they wouldn't impact price much. The more hashes they contribute, the fewer total coins there will be per day.