If all of your sites link to each other (even if they only link from one page) and are pretty much about the same things, then I'd call it heavy cross-linking. But if each site is about a distinct sub-topic, then I wouldn't.
For instance, let's say you have a main site about widgets. You could have another site that is all about blue widgets, and another one that is all about green widgets, etc., and the sub-topics wouldn't overlap much at all. Then they could 'naturally' link to each other. But if all the sites contain the same sort of stuff, even if they are designed differently, then it would be right to say that only one site is necessary and the others are just there for the linkpop/pagerank.
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I'm not suggesting that you get rid of linkpop/pagerank sites. If that's what it takes to get to the top then do it. But you must be able to accept it if they all fall down.
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