No one buying followers wants "eggs" which is what they call the default twitter profile pictures. You will actually see people advertise, "no eggs." The pictures and tweets are scraped from other users either randomly or based on keywords to make the profiles look real. It's sucks for the people who get scraped, but that's what's it's like in that world...
Research-grade bots typically combine this with some logic like taking tweets from sources external to your current network graph, or trying to keep the bot's persona reasonably self-consistent. E.g. see the RealBoy project:
http://ca.olin.edu/2008/realboy/
Spam bots generally have a much lower bar. The majority seem to just use a follow-back paradigm, i.e. they put some spam message in the user profile, follow people at random or according to some search parameters, then unfollow a couple days later if you don't follow back - this last, since Twitter decides you might be a spammer if you let your following/followers ratio get too high.
I've been doing some work with Twitter followers recently, to try and estimate real followers versus spam accounts. So far, I'm seeing something like 15% real, using relatively simplistic spam detection (likely high error).
I'm mainly looking at commercial accounts with five-digit follower counts. I also haven't run enough yet to know if the result is more up to my detection routine, or if I'm choosing accounts that bought followers at some point, or what. So don't take it as a general rule (yet).
Yes, those accounts ARE fake. No doubt about it. And they keep tweeting and re-tweeting each other because part of the requirements on buying Twitter followers is that you want ACTIVE Twitter accounts. Accounts that are doing something on Twitter. So these Twitter bot accounts are fake AND they tweet fake garbage so that the Twitter automation software people run doesn't flag the account as fake or inactive. Thus you have a legitimate fake bot account you can use in your network if you're selling followers.
It doesn't make it ok, but it's the state of things online. Everyone wants followers. They want Facebook fans. They want likes, +1's, and re-tweets, and Web site traffic. All of which can be bought, and quite easily too.
https://twitter.com/search/realtime?q=Lil+sis+is+up+coughing...
Interestingly, with each search I'd click through to the user account, search for another of the tweets made by the same account, and find yet more unique fake accounts. I started compiling a list, but gave up when it reached a few hundred.
https://twitter.com/search/realtime?q=Record+time+from+home+...
My theory is that almost every account linked to one of these accounts is fake. If you take any of their tweets you'll see them repeating the same tweets across a large web.
I'm going to forward this to my daughter) who is very ecologically conscious but overwhelmed at the immensity of the issue) as an excellent example of how they can make a positive change.
Thanks again.