Dislike using namespace std?

It seems as though more experienced programmers tend to write code with std::cout, std::string, etc., whereas less experienced programmers always write using namespace std;. They also tend to assume that, in code snips, it is already included.

Why is this? If it's a dislike, what's the problem with it? As stated in the namespaces tutorial on this site, a namespace can be overridden if need be. Is it the case that you have written your own namespaces? Or that you so seldom use things like the STL and stdin/out that it just isn't necessary?
When I see cout in someone's program, how do I know if it's std::cout or some other user-defined variable called cout? I have to read the whole thing.

While that is a word that's unlikely to be used as a variable, how about count, begin, swap, copy, remove, array, max, or ignore? (all those names exist in namespace std, in different headers, but standard headers may include other standard headers, so I can't just look at the list of #includes)

Is it the case that you have written your own namespaces?

For a one-off forum post, no (and using namespace std; is just fine in a small .cpp file), but at work, there are hundreds of namespaces, some three or four levels nested. Any using declaration would make things far too confusing.
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Well... this is pretty much what Cubbi already said, but by someone else.
http://www.parashift.com/c++-faq/using-namespace-std.html
So, instead of
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using namespace std;
/////////////////////////////////
cout << "Foo" << endl;
using myOtherNamespace::cout;
using myThirdNamespace::endl;

You'd rather see
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std::cout << "Bar" << std::endl;
myOtherNamespace::cout // plus whatever it does
myThirdNamespace::endl // plus whatever it does 

Now that I've typed it out, I realize how much more typing it is. Aside from being less than clear which namespace you're using. Thanks for helping me realize that.

But now I have a question. For nested namespaces, how do you specify which level you want?
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// Like this?
outerNamespace::innerNamespace::someVariable
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Someone on here a long time ago suggested I use std:: and since I have been in the habit of doing so. Now I do not like cout cin etc... without the preceding std::
Perfect example of why this is a thing:

std::distance
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