Twitter – How to block all followers except followed

I have ended up using these lists by Twitter:

• Developers
• Engineering

You're generally right - For the most part, you're looking at completely 'Bot' accounts, particularly for "high quantity purchases". Even though you can usually identify bot accounts, they're almost entirely pointless because they don't do anything. Without actual engaged followers (RTs, @mentions, etc.), the high count does very little.

Lately, there have also been services popping up for 'Getting Paid to Tweet' and follow. For all practical purposes, people can 'rent' their Twitter account to ad agencies to do with what they will - depending on the influence of their Twitter account, it may be slightly more effective, but more than likely just opens the door for the creation and rental of more bots.