I agree not to re invent the wheel
but portlet 2.0 is the time for every one to reinvent the wheel
and for us Iranian developers to show there are some good developers in Iran too (may be is not!?)
we are not force to do every thing from scratch
we may start with a portlet container then move into a complete portal.
we can use some liferay  and other open source portals code in our own code.