is the same as <xmlns="MSList:http://www.microsoft.com/schemas/rss/core/2005"> <MSList:blah/> The prefix is just used by the parser to map back to the namespace URI. So long as the URI is correct, and the prefix is used consistently within the document, what the prefix actually is doesn't effect the end result.
To the parser, no, the value of the namespace does not matter if it is referenced consistently within the document, but then again, neither does the element name. You could have
<a:b> instead of <simplelist:listinfo>, the point was to make it easy to understand without having both the parser and the developer to read an entire schema.