As per my knowledge any Project is a good fit, provided you have the right people and and can make enough investments. Giants like Yahoo, Google etc all have there Portals. So it depends how much can you invest both in terms of time and money.
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Is there a significant investment to be made in people/training/time?
If you go for an open source Portal solution like Liferay then the cost will be considerably less. Still as you said, you have to hire good developers to do the job.
And that might be expensive. Or you can use services of already trained/experienced consultants to do the job for you, if you are not hiring. But its always good to hire 2 good developers to do the job than 10 of them who are good for nothing.
But going for a Portal Solution offered by say IBM will mean quite a big investment.