Exactly, jcorkern, about URLs!
But now think about it - any time you reciprocate links, you create more links on your site. Usually people have 20-50 links on one page maximum. Otherwise it's about too many outgoing links on one page - it's not a disaster, but...
With some solutions it's possible to build dozens of thousands of links (I am not talking quality, only quantity at the moment). And it means if you are splitting links into 20-50, you get hundreds of new pages in the link directory. And this is where we come to URLs.
And now the best part of it. I think more and more innovations that Google introduces into its algo will be about telling natural sites from unnatural sites. One of the factors - the speed of link building. Let's be fair - can a real site get 1000 backlinks overnight? Almost impossible: you either have to be famous marketer with huge base of people who agree to backlink
or you must have some friends - top markters with huge bases
or great press release (something like - time machine was invented). That's it.
So, Google in the persuit for helping natural sites and slapping on manipulators will be putting some limit. If they did it for URLs (which is funny), what can stop them from doing the same on shameless link building (which is more reasonable)?
That's why my moto is -
keep looking natural and you will never have any problems with Google, because Google will never fight natural sites.
And with link building looking natural is also ok. I think up to 100 backlinks a week is more than ok to look normal.
P.S. I am not on top, just #9 for my link exchange keyword, but still not bad
