Where does Cerberus (Smokey) come from? Is he an anomoly of the island?  What if he is a security system of the island put in place by the Dharma Initiative to keep the hostiles away from Swan Station.  This is would explain why the hostiles stayed away from Swan and not totally privy to what goes on there.  It would also explain why Zeke would of drawn a line in the jungle, to keep the losties out, but also because he knew that is only how far the hostiles could venture without waking up Cerberus. Now in another theory I think that the injections Kelvin and Desmond were taking were an antidote to the darts, but could it be that it is something that lets Cerberus know not to go after them when it senses it in their bloodstreams? Not only would Cerberus keep the hostiles out, but would also protect the DI personnel.

Interesting - yes that would make sense. That he was designed to keep the true Others, the Hostiles, away from the DI personnel. Maybe Smokey can become an ally of some sorts? Would this explain why he didn't hurt Locke?

Now the island told Locke to rescue Eko, which he did just in time as the bear was about to dine on Eko.  Does that mean the island had Eko rescued so he could just stand in judgement and be bounced around by Cerberus?  Or is Cerberus controlled by some other entity other than the island...perhaps by another hatch or by the hostiles.  Eko did take out two of the hostiles and they seem to like to exact their revenge.  

Or is it that the Island would like to evict Cerberus from itself, but only has limited powers so needs the Losties to rid itself of Cerberus and the parasite hostiles?

We almost need to know which side Cerberus is on to figure it out.