Meh. Doesn't seem any more offensive than a targeted ad on Amazon. It's just a favorite, after all. A subtle, "Hey, check us out." These
are company/marketing/publicity accounts anyway (I'm assuming). It's not like followgen is masquerading around with a stolen identity like most follow bots, spitting out bit.ly spam with suggestive tweets and racy pictures. It's simply programmatically allowing twitter accounts to reach out to people who happen to fall into a statistical category. It's also important to remember that follow bots make it easy to follow-back via the "follow" link in notification emails. On an iPhone, to follow the account of someone who favorites my tweet I would 1) see the notification, 2) open the app, 3) select the interaction 4) select the user 5) follow the user (I count 3 interactions using the web app, already having the page loaded). If it truly is spam I can just ignore the notification, as opposed to having to block and report a follow bot.
Rather ingenious, if I do say so myself. The favorite interaction has become increasingly important over the past year or so... I know friends (non-technical friends) who joined twitter recently who would rather get a favorite than a retweet, as a favorite feels more personal. This opposed to a retweet, which seem to be given out much more frequently than a year ago. It would also be pretty cool to be favorited by a recognizable name. Now that I think about it... could be a pretty useful recruiting tool, if targeted properly.