Possible but not recomended. Microphone stands are not built to support that kind of weight. I would sell the mic stands and get some real lighting stands, they're not that expensive. Always think safety first. Mic stands also don't have the outrigger support like light stands do, and a mic crashing to the floor dosn't pose the same hazards like certain lights can (like starting a fire). I'm all for DIY but that's one I would tend to skip...
I use them, and the other way 'round, but not for anything heavy. And even if you drop a CFL bulb it is a huge mess. Light stands are not expensive, and you can use them as mic stands.
I take one simple approach to light stands and such: screw the light, if it could hurt a crew member then it's not happening. I mean of course there have been times when we've jerry rigged CFLs or china balls to random things but just use common sense. It does depend on the lights you use but remember, a fresnal can seriously permanently injure someone if it falls on them. You might shatter a lens or globe but you might also kill someone. If it's project specific, just rent. I barely need mombo combos but when I do they're dirt cheap to rent.
Deniz hit it right on the head: safety first. Lights should always go on the best stand that you can afford and each stand should be properly weighted down with sandbags. Taking shortcuts and trying to jury rig stuff are just a great way of asking for an accident to happen.