Correct. You cannot delete receiving addresses. Doing so has no benefits, and would cause you to lose all coins you ever received with that address, as well as any coins you might receive at that address in the future, hence the software does not allow you to even try to do this.
Why do you want them out of sight? Are you never planning to receive anything to any of those addresses again?
Not yet. I have a public address for almost every Bitcoin account i use. I imagine there will possibly be a time when some of these websites will die and my address book will just more cluttered than necessary.
You can always change the titles of the addresses as well. I've "recycled" a few of my addresses like that to keep things clean.
NP! Just as another heads-up, any transactions you've already rec'd with an address will still show the previous "description," so you don't have to worry about confusing your incoming payments either. Ex. if you had one named "Incoming" and it had gotten 0.01 BTC and then you renamed it "Incoming#2" and got another 0.01 BTC, they would each, while having the same address, show their respective description at the time the payment came in.
