Here is the ONE thing that I feel Apple did wrong in photo stream.
You cannot delete any individual picture from your icloud. It is an all or nothing deal. If you take a photo that you do not want to keep for whatever reason, you have to delete the entire library.
Go to www.icloud.com and go into the advance section to reset the stream. Then go to your idevice and go into Settings > Photos and turn Photo Stream "off", confirme delete and then turn "On" to start it again.
If enough people make noise Apple will get the hint and will update this feature so that you can delete individual photos.
Currently you can't. Once a photo goes into your Photo Stream, it stays there!
iCloud manages your Photo Stream efficiently so you don’t run out of storage space on your iPhone, iPad, or iPod touch. If you have Photo Stream enabled on your iOS device, every single photo you take appears in a special Photo Stream album that holds your last 1000 photos. You can’t edit or delete photos from your Photo Stream. If you want to touch up a photo or keep a favorite shot permanently, simply save it to your Camera Roll. iCloud stores new photos for 30 days, so you have plenty of time to connect your iOS device to Wi-Fi and make sure you always have your most recent shots handy.
Not exactly. If you are using IOS 5 here is a direct solution to your problem. Take your iPhone or iPod touch, and go to your settings app. Scroll down further and click on iCloud (it should be right below general) Once you click on iCloud there will be a list of options like contacts, mail, etc. scroll down until you see photo stream. Click on photo stream and click off. An option will pop up telling you this will delete your photos. Click delete photos. NOTE: THIS WILL DELETE EVERY PHOTO YOU HAVE IN PHOTOSTREAM.