Without an exploit, the most followers you can have at once is six:* one for every 4 points of Charisma (up to five, at 20 CH) and one more for Persuasion expertise.
Another benefit (as recently discussed
in another thread) is that Persuasion mastery means you can recruit any follower regardless of alignment, and 20 CH means they won't leave on their own, no matter how much they dislike your actions (or another follower; some combos, such as Raven and Z'an Al'urin, are like oil and water).
And as Waltorious pointed out, such a charismatic build means you'll also open up dialog options to avoid a number of situations that would otherwise have to be solved through violence.
The downside to letting others do your dirty work, however, is that you'll level up more slowly; you don't receive as much experience from followers fighting as when you get your own hands dirty. Not a big deal, especially since the game caps you at level 50 anyway (unless you use the level cap remover mod).
And as pointed out in
another recent thread, there are options to increase your Beauty and Charisma through finding or stealing items, rather than by spending points, if you know where to look.
*Not counting "free" followers, such as Dog (the "worthless mutt" found in Ashbury), temporary hangers-on like Doc Roberts or Thorvald, and any summoned creatures (including the familiar you can conjure from the spell of the same name).
grecza: I have noticed when I have become a more technicaly oriented character magic healing by Virgil had no effect on me... should I also pick herbology from technological disciplines, so I could make healing potions for those more technicaly oriented followers, or will I be able to heal them with magic anyway ?
It's a good idea; and if you're already investing in Intelligence for tech disciplines, then the Healing skill is another viable alternative. (It does require stocking up on bandages, though; and at low skill levels, is about as useful as low-level firearms.)
The more tech you or any given follower is, the greater the likelihood of spell failure — even beneficial spells such as Minor Healing. Virgil and potions will still work on non-tech followers. (One notable exception: Essence of Intellect seems to work for you, no matter how tech you are. Good thing, too, when trying to craft high-level schematics with the minimum number of additional tech manuals.)