Which Photo Sharing Site Should I Use?

I am starting a search for a photo sharing site. Currently, I am using flickr and it has suited my needs up to this point. But I am running out of space for my free account. I am going to evaluate more sites before buying a pro account.

Here are the following requirements that I have:

• Store unlimited amounts of photos
• I want to be able to link to the photos (hosting)
• Photo streams or sets to organize photos
• Tagging
• API
• Ability to view photos without registration (difficult, I know)
• Ability to purchase photos (preferably in matte)
• Active user community
• Public and private spaces

I am willing to pay a reasonable price for these features. I know flickr has a lot of these features but to me it seems more of a community site. I personally do not want to share every picture of my family with the world. I want to make sure I choose the best site for what I want.

Are there any features that I should look for? I am sure I will come up with more as I begin my search. Also, recommendations are welcome.
I will post details as I do the search. A word of caution: it may take a while (a few weeks).