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Every extra link placed on a links page means less Pagerank pass-through for the other pages getting links from that link page (and that could be a site- internal page).
Do not forget to link out though. [webmasterworld.com]
The question in my mind is whether the curve for PR weighing is as steep as the curve for the Toolbar. It think it must be pretty steep, else I'm sure the top PR sites would rank high for every word they use.
If so, then loosing half your PR won't make much difference to the rankings or the Toolbar PR.
I'm coming from a different perspective though, if you decide that you need PRn to rank well for keyphraseX, then a 50% loss of raw PR due to a links page shouldn't affect your predictions much.
This is why I think that people worry too much about feedback loops, they make a big difference if you're modelling raw PR but they don't have anything like as much affect in terms of sites getting listed under phrases.