And even Microsoft do it on MSDN.
What am I on about?
Posting code that requires importing a namespace - without specifying what namespace(s) need to be imported.
Imagine the following code:
Stream stMyStream = new FileStream("SomeFile.txt", FileMode.Open);
Now I know, and you know, that Stream exists within
but without a using directive at the top of your file, the compiler doesn't know this and it gives you a whole bunch of red squiggly lines.
In the above case it is obvious which namespace you need, but that isn't always so, and you can be left scratchign your head for ages trying to track down which namespace you are missing.
So please people: when you post code example - either use a fully qualified type name, or specify the appropriate namespaces to be used.
System.IO.Stream stMyStream = new System.IO.FileStream("SomeFile.txt", System.IO.FileMode.Open);