The other thing Flickr has going for it is they're still the ONLY one out there that has decent support for metadata. I've tried Smugmug, I've tried OpenPhoto, I've tried Gallery (v2 and v3), and Flickr is still the only one that seems to understand concepts like (for instance) "the tag 'Joe Schmo' should not be displayed or (god forbid) SAVED as 'joeschmo'".
And nobody but Flickr has the (really, really great) Guest Pass feature, where you can share private photos with people WITHOUT forcing them to sign up for something.
There's even more features that Flickr is the only service to have. They're ahead in many areas but the speed at which they've been adding new features is significantly slower than others.
It's just a matter of time before other services replicate the features Flickr has today which are valuable. Remember, they've been around for 8 or so years. It takes time to get to where they are today. But 8 years from now, it won't be Flickr we're talking about.
And nobody but Flickr has the (really, really great) Guest Pass feature, where you can share private photos with people WITHOUT forcing them to sign up for something.