I want to be able to destroy them, because I don't like the idea of being bound to the Nightingales. I sent this idea, probably as many others have, to a Bethesda worker, who then told me to go put it up in the forums, so here I am. This was my message to the guy recieving my mail in Email Support: "You should add an option to destroy The Thieves Guild like the way you can destroy The Dark Brotherhood. This would be a lot of fun, and could really make the game even more enjoyable, especially for those who don't like the idea that you're bound to the Nightingales after death and all that. Thanks!" This was the answer i got:
"Hello,
Thank you for contacting Bethesda Technical Support.
As we - in Technical Support - are nto actively involved in the games development process, I'm afraid we are unable to act directly on your feedback on Skyrim.
As several members of the development team regularly visit the official forums, a better place for your suggestions, would be here, as they would be able to act on this and give you feedback.
Best Regards,
Michael D.
Bethesda Technical Support"
So here I am, Bethesda! I hope you will take this in consideration for future updates!