You all are a creative bunch. I just thought I'd throw this question out there to see if anyone had some interesting ideas.
My own theory on the matter is that only Nemesis can ever control the Smoke Monster. Those couple times when Ben went into his little secret chamber and seemed to summon Smokey, I believe, were simply opportunities that Nemesis took to make it appear that Ben had any power. For example, it sure seems that Ben called the Monster to epically F-up Keamy's men after they shot Alex, but I'd like to put forth the idea that Nemesis simply wanted to drive off the mercenaries anyway, to allow Ben time with his dead daughter (to REALLY let it sink in for him), and then allow him to escape. This set up his "judging" by Smokey later and of course, being commanded by "Alex" to follow every word Locke said.
I don't think that the Monster is "feral until summoned" either, because if it was, there'd be a lot more Monster-killed Losties by now. I think Nemesis is ALWAYS controlling it. People like to point to the first episode and say "Well what about the pilot? It just murdered him for no reason! And it was gonna kill Jack, Kate, and Charlie too!" I highly doubt it was gonna kill the A-team members... probably just scan them, like it did with Eko, commanded under Nemesis' orders. As for the pilot, remember who was supposed to be flying the plane? Our own favorite "candidate" Frank Lapidus. Nemesis knew that the pilot was useless and thus had Smokey bump him off.
Another time people point to about the Monster's supposed wildness is when it chased Kate and Juliet (when they were handcuffed), only being stopped by the tree they hid in and the sonic fence. But come on folks... it's made of smoke and it can loom up like twenty feet off the ground: it ain't gonna be stopped by a tree or a ten-foot fence. It was chasing them to scan them, and it succeeded with Juliet, but it wanted to finish with Kate.
Finally, and most memorably, people say Smokey was gonna pull Locke into that hole to kill him in the Season 1 finale. "That Dude That Was Sucked Into the Turbine" put it elegantly in the "What if..." thread: "We saw Smokey pull Montand in despite the efforts of the team, but yet Jack was able to hold Locke up." I don't know exactly what it was gonna do with Locke, but clearly it wanted him alive, most likely to bring him to Nemesis. When Locke "...saw the true heart of the Island, and it was beautiful" or whatever he said, some people think that maybe he saw a white, Jacob-controlled Monster (let's call it the Mist Monster). I don't believe in a Mist Monster... I think Locke saw the scan flashes, which blinded him in a sense to the Monster lurking behind them.
I'd like to conclude by stating my opinion that if more people stood their ground against the Monster instead of fleeing (although I can't blame them), then we'd be treated to more scenes of people being scanned, and possibly then released, instead of a savage Monster killfest. I'd like to conclude this conclusion by stating that Savage Monster Killfest would be an awesome band name.