Well, it can be a pain in the butt if the DM allows it do be so. Example: Having a group of six players and allowing them all to take Leadership. However, in our group, at least, we use it to fill in the minor roles that no one else had taken. Like if we have two fighters, a mage, and a rangers, eventually, we'll be like 'crap, need a healer. and possibly a rogue.' So what happens is that someone gets a cohort which becomes a healer, rogue, or sometimes both.
HOWEVER, what we've started in my group is that you can take Leadership, but you can only grab an ally or someone who looks up to you. [sounds like it could be annoying, but if someone wants to take leadership, they tell me a class or basic concept, and I'll work within the next couple of gaming sessions to add in an interesting character they will wish to have as a cohort. Sometimes this is obvious and other times not quite so much]. No one has complained much in my campaign. The choices so far were: an archivist love interest, a glass figurine rogue/cleric [odd how that came about, but it did], and a Modron favored soul.