I imagine that in these specific case is because longer URLs represent deeper pages on the site that are less "important" (in terms of internal incoming links and pagerank) than the shorter ones. It doesn't seem logical that google order the URLs by length and then crawl them in that order; probably the URL length can be a factor that the bot takes into account, but not the only one in the manner this article suggest :)
Anyway, good point, that deserves more testing to extract some conclussions
If you add your social profiles to your google profile, Google will add all your contacts in those social networks to your "social circle". Also your gmail contacts, or people you follow on google reader and so on.
Gmail has started suggesting friends to 'consider including' on emails. Personally, this has resulted in both me and my ex getting some very uncomfortable suggestions recently for whom to consider including in correspondence. It hasn't suggested we email each other, which would be forgivable, but a third party whom I had never directly emailed. And it highlighted for me what I consider to be a major problem with Google's social initiatives, which is that they've collected and employed this 'social' data in a completely antisocial way--behind your back, when you're using unrelated services. And it might be clever, but it can get very creepy.
And this is one of the pitfalls of testing things internally at a company like Google.
There are a lot of important use cases in social networks around "me and my recent ex", but within a corporation you'll be unlikely to run into them. (Similar issues caused a lot of complaints for Google buzz.)
I don't think the suggested recipients feature pulls from other users' contacts. You, your ex, and the third party have probably been recipients of the same message in the past.
Anyway, good point, that deserves more testing to extract some conclussions