All structures and ships in this game that you can own can be scuttled.

Scutlling structures can make sense. Most people scuttle their capital ship factory because it brings a nice boost to the economy in the ealry stages of games. You can also clear slots for a different type of building.

Sometimes, it makes sense to scuttle a type of ship if your opponent has massed the ship that counters it (like if he has an lrf spam and you have an lrf spam urself but also a few light frigs, scuttle the light frigs to get some resources, open some slots, and get something else, like fighters)

Scuttling planets, however, almost never makes sense. What's frustrating is I catch people who scutlle planets. Somehow, I never manage to be the guy who's attacking and finds someone dumb enough to scuttle their planets. I'm always the guy who has an ally "Hey, I'm going to migrate, I'll go get another system to myself! And when I leave, I'm going to scuttle my planets!" Ugh.....

Never, EVER, EVER scuttle a planet. It's a source of income. Need I say more?

If your enemy is sieging you. You make his life so much easier by scuttling. Instead of having to wait for his capital ship(s) to finish seiging before he moves on, you give him a HUGE freebie and sign a death warrant not only for you but most likely your allies too.

I can think of only two scenarios where scutlling your planet can make sense.

1) Your ally has been cleaned out, has managed to escape with a colonizer, and needs a planet. You can scuttle a planet in your empire (preferably towards the fringes where the allegiance is low) and let him re-establish himself, b/c a human ally is normally better than an AI.

2) If you have a scenario where you and an enemy are going at it, both have huge established empires, there's one way this can be a stragetic advantage. If he has cleaned out your grav well (before he gets the mines), and you've retreated, and you already have your fleet ready on the next planet, take a look at what type of capital ship it is. If it's the colonizing capital ship (it almost always is), scuttle the planet. That capital ship will more than likely automaticalaly colonize the planet, and unless he's paying attention he may miss the fact that he was being taxed for a ahile.

You hurt his eco, which in turn hurts his ship production, so you can play a little catch up. Also, since your mines are still there, he can't build his own to help negate the masive spending that was just incurred on him.

It's rare this situation will pop up, but it can be useful.

I'm open to suggestions where scuttling planets can actually be the right idea.