*sighs*
Look the costs associated with such a network is huge, in time, maintenance and upkeep costs. I have a private high PR network, but it's relatively small (120 or so domains).
You find them to be highly effective? I find them to be completely ineffective, and have always been disappointed by the results from my domains when adding articles. Great for medium competition keywords, but there are free options (like above) that provide better results.
I have a small (compared to others) network of about 140 sites- nothing lower than pr3- pr7. Always great PA/DA, huge BL profiles, and many are authority sites (think chamber of commerce sites, city and municipal sites etc etc). Some of these sites will pass juice, while others do not. I made the mistake of selling some links on a few and even though I kept the OBL's low and did them contextually, the value of blog or rather site network links can be weak at times. The sites often don't get deindexed, but it's obvious when Goog takes away the juice/benefit of said sites when they identify them as spam sites. Always separate/unique IP/hosting/DNS and diverse OBL's.
I find one of the best benefits from site networks is using subdomains, which pass age, and then adding articles and maybe one link. If people buy dropped domains and then subsequently add 5-10 links on the home page, it's pretty easy for goog to ID the site as a spam site at that time, even if they rebuild the site as it was prior to the drop or renew.
Generally per domain, if you build the network from new sites, it'll cost you around $22-25/year (if you stack them 3 per IP, you can get this a bit cheaper)... my bots cost me next to nothing, and achieve far better results in other search engines, like bing and yahoo particularly (and honestly, still better in google as well from my recent work). If you buy them, tack on another $10-15 to this figure per domain. So to compete in my niches with the big boys with high PR networks (who all buy their links, besides 1 guy) you'd need 2000 or so high PR blogs, and have a $500-700/mth bill just on hosting. Sure, you may consider $80k on domains first year to be nothing, because I made 6 figures during 2 months of the 2012 year, but alas... that is still a lot of money to little ol me.
I wonder what could possess me to drop what I'm doing now, which is working and making great money again, and go back to thinking about large blog network construction... However, I've watched google murder sites who have done this, and their networks (though still indexed) provide no google value to their sites any more post penguin. This has caused a huge amount of hesitation for me about expansion and I have gone a completely different direction.
People always say "oh my blog network is powerful"... well it's not... not really. A few hundred domains will do some good things, sure, to medium comp terms... I use mine often of late for this after running my tools on sites. Site networks, when set up correctly, will continue to be the way to win the game, IF the end game is monetized to the point where it makes sense economically.
Just look at the most competitive serps and still you will see quite a few using this technique- very hard for goog to ID a site network, especially if it is relevant and the setup is kosher.
A few hundred won't get you far where it counts...
Unfortunately there's no easy way to set up 200+ high PR network, so tack on costs for hiring this out as well... You can post spun articles to it, but I've always disliked this idea as well as it's a very large risk in the long term. I'm not sure about you, but if I had online infrastructure that costed as much as a house (every year!), I probably wouldn't be posting crappy spun content to it.
Also, the images I embed are from the site I'm backlinking.
Perhaps post penguin a network is the answer (seems like xrumer with mods is working really well too for temporary gains), but I'm loathe to admit to this at this time. I have said extensively: "I am no longer committed to the effectiveness of these methods"
At any rate, I think the most powerful way to backlink now, from the results I've gotten myself (this is only for google of course) is combinations of dynamic pyramids across tons of tier 1 types, and a lot of manual d0follow comments. Then you throw your network on top of that.
