Ok cross purposes.
Find for indexing is one thing
Discover it was a private network is another.
Yes - it could - or at least make an assumption that it was based on evidence that a less than thorough set up might leave behind.
A 20 node network using 20 cheap hosting accounts with domain privacy (Google are not allowed to scrape ICANN or WHOIS for commercial reasons - neither is anyone else - but privacy is still a good precaution)
Each node costing say $60 a year for they domain and the hosting. Not using the same CMS on them all, not starting them all in the same month, not posting the same content on them all (or spun versions of the same) creating outbound links to sites other than your own, rarely selfishly linking. Updating now and then, adding multimedia - being consistent.
If you do all that Google SHOULD never know. The way I'd do it would be to build a node a week for 20 weeks, spread the cost and the footprint. Use mostly aged domains some new ones. It's not rocket science but it does take some application and consistency, and is worth it if you are use 1 or 2 sites to make your cash. Obviously this is not really a tactic for micro site or churn and burn guys really. Though I wouldn't be surprised if some did a variation on this somehow. Over time you could add some good free sites to it as well (Tumblr, Blogger, Wordpress.com), maybe end up with a 30 node network? Worth considering.
Scritty