limit on reciprocal links between sites

Does Google set a limit?

[yodakiteman]

We all know that reciprocal links between domains are good.

My questions:

1) Is it good to have multiple links between domains? (assuming each link is unique)

2) Is there a recommended limit to the number of reciprocal links between domains. If so what do you think the limit is, 1, 5, 20, 100?

It may be logical to have hundreds/thousands of links between sites, if the sites are well structured, but I suspect Google may frown on this.

Any opinions appreciated.

Thanks
Matthew