The Leadership Feat
Some aspects of the Leadership feat are redundant under my campaign rules, as the Entourage feat (that you picked up as a Bonus feat at L2) along with the staff employed in your businesses and estates represents your followers. However, there are still many benefits to taking the Leadership Feat.
Cohort
Most importantly, you get a Cohort using the guidance (and modifiers) as per the PF description of the feat. Your Cohort does not count against your roster of Entourage-Assistants, Entourage-Cousins or Entourage-Allies.
Followers
Many of your followers are represented by staff who run your businesses, manage your strongholds, sail your ships etc. The vast majority of these are nameless followers, who go about their daily routine, who understand that what is good for you, is probably good for them. Most of them are L1, L2, L3 commoners of one type or another.
Your more important followers are represented by your entourage members - they are all named, have their own character sheet, and can take part in Fuzzy and General threads. They all have more important NPC classes and the potential to advance to higher levels - although they probably max out at Level 6.
Any extra followers are made up of contacts and people who deal with your businesses / strongholds.
You can use your Leadership Score (for followers) when calculating the maximum number of Entourage members you may recruit. If you already have a home base (such as a stronghold or a mansion) somewhere, you get to apply the appropriate +2 bonus to your leadership score.
Using Followers
Followers are not a private army, unless you build developments with defence points - in which case the soldiers stationed there are, effectively, your private army. Others might, in extreme circumstances, turn out to help physically defend your property - but generally they just go about their day-to-day business the same as anyone else.
However, they may well pass interesting information up the chain, using your named entourages, either via gossip or as a deliberate action. However, that is primarily a DM driven mechanic, although you can solicit information from your followers, via your named entourages, IF you have followers with the right skills in the right region. If you own a magic shop, you might try and find out about magical disturbances, if you have any building in an area you might try and find out some minor pieces of Local Knowledge - such as the best place to eat, who is behind the local protection racket, what the competition are up to. It will only be rumours, of course, but it might well give you a starting point. :)