Dragons and Balrogs

One more point on the subject. In The Silmarillion, it happens to mention that, of all the creatures of evil, it was only dragons that Sauron could not control. Hell, that sounds like dragons are pretty damn powerful to me. And if he himself could not control them, there is some allusion to the possibility that they were immune to the insinuations of the Ruling Ring, which is most definately saying something.
Of course, since dragons have that bit of magpie urge of theirs, they might have taken it anyway if they'd found it.
Another thing, I wonder- could dragons pick and choose their alligiences? In one of the Lost Tales, Farmer Giles of Ham, the green dragon Chrysophylax becomes friends with a mere, rather puny, human farmer (or as much of a friend as a dragon could make himself), and, in outlining for future stories (which were never written) mentions this green dragon protecting and even rescuing him, which are qualities one would assign to more benevolent creatures.
In the words of a friend, following this question:
"Well, some are better or worse than others."
Makes you think....