There's so many exp camps, I don't see how this hurts 'real' exp parties. The problem there, in my opinion, is that it's been so long, now that we finally do have a search function, most people have already leveled most of the classes they want to play to 50. That, or they're finished. This isn't really plings fault, persay, as just game-age. The level cap will be raised, and then, it won't really be viable to power level people lower than 40-50 anyways. (which are really the levels that matter, imo)
I have pl'd some friends on occassion. Not terribly extensively. We usually go and kill things that are good farm material, or have low amounts of aoe. So it's usually 'Hey, I'm going to go farm wool. Why don't I take my friend along who's been doing leves for two hours and can't get an exp party with me, and help him get some levels while I do this?' Then we wind up with a bunch of people hanging out and bsing in team speak for an hour or two while we farm wool and help so-and-so get some ranks. Oh, and wait around for Uraeus to spawn in between. Or whatever.
The act of power leveling takes up someone's time. If people prefer to have their friends power level them, and level up that way, so what. If the power leveler is willing to do it, then that's their choice. There will be plenty of party content in the future. Yes, this can be taken advantage of by people who want to shovel gil at it, but if you're getting your linkshell members to pl you, they probably friends or they're returning a favor, or what not. I'm certainly not going to go out of my way to go power level some random person I've never spoken to, or someone who sits in town /shout'ing stupid stuff all day.
To be honest, I see very little pling on my server. And when I do, it's usually two friends, or a few linkshell buddies in other LS's, helping each other out because they're sick of doing leves, or they want to hang out and chat while they're doing something semi-productive. I saw giant PL parties back when the system was screwy for like two weeks, but that's long gone now. I think we'll see a few updates to the system to address any 'issues' (if it's not working as intended) with being able to pl other players.
My only real beef is when being power leveled causes skill problems, and a person insists on coming as a specific class and they have no idea what they're doing, because they were power leveled to 45 and haven't even set up their ability bars properly yet. At least understand the mechanics of the class once you hit 50, so that you're not causing others to be bogged down by your ineptitude in the class.