How does Google penalise heavy cross-linking?

Have done it for years, and only recently somebody pointed it out.

[killroy]

I have a website, a directory, that has been crosslinked heavily wit hanother domain for many years. Basically the two sites are two different interfaces for the same data. One is a slimline interface, bringing up only summary information with quick searches, while the other one has a complex categorization and expanded information on the individual entries.

The sites are quite unique, in that they are marketed to different customers. The former is the poor mans version of the later, while customers of the later site are automatically included in the former.

Users use the slimline version for fast results, and the other one for leisurely browsing.

Their relationship can be compared to that of google and yahoo.

Now each category in the one links into a search on the slimline version, while each entry in the slimlien version has a "more details" link into the detailed entry page on the bloated site.

The bloated site (around for 3-4 years) is a PR6, while the other one is a PR5 (around for 1-2 years)

Now somebody has pointed out to me that the crosslinks are deadly, which are a great concern to me since there are literally 1000s.

I have removed them now, but I wonder how these have influenced the PageRank. Is there such a think as partial penalisation, or was I simply lucky not to have gotten a PR0 penality already?

I appreciate any light shed on this.

S. N.

[hitchhiker]

There is much debate on this point..

[webmasterworld.com...]

[killroy]

Thanks for the pointer, hitchhiker.