On the Group/Solo cost of living.

I group. I solo. I duo. I've staticed. I have raided, taskforced, pugged, warbanded, fleet maneuvered and run around like a headless chicken in an Escher painting.

I understand that an MMO has people. I know that even when I run alone, there are people. I accept that when there are people en masse, I sometimes wish there wasn't. I play what I'd like when I want and do what I can for the mass when I can.

At the end of the day however it depends on my mood. I've seen people who group more than anything not log on when they have a bad mood. Why? So they don't take it out on others. Noble that, but the alternative is you could play your game still and just not play with other people.
I've seen hardcore soloers complain about new group based content essentially locking them out, but guys if any random schmoe could solo the content, we'd all be bored fast.

I think the reason Groupers hate Soloers is the old old old player type, the Tank Mages. Tank Mages either want or have the ability to carry the game on their shoulders. They can solo every boss that ever wiped your team, they don't need heals or dps or (de)buffs as they have them themselves. They don't need you. In social games and online spaces where depending on others is promoted, this can be a bit jarring. Especially if you need the Tank Mage so your group can do things. Not everyone who prefers to play alone is a Tank Mage though, just as how not everyone who only ever groups is a powerleveller.

In City of Heroes, I soloed every Kheldian arc. Why? Well.. as much as I love my friends and as much as I enjoy playing with new people, you lot get in my way when I am playing for the content and fluff. You want to do this mission and get to the next as fast as possible or roleplay something that will slow me down or make the fluff whore in me cry quietly.
In Warhammer, when I am not feeling up to the mania of a Warband or the banter of the guild and groups, I go and solo. I can take my time reading the mission text. I can suicide repeatedly if I so choose. I can play NinjaDwarf and get into places I really probably shouldn't. Nothing in that playstyle is bad. I am not saying you cannot come and mission/quest with me, I just want to take it easy and am not offering you a fast and productive experience.

Am I drain on the Sentinels in Warhammer? I like to think not. Through taxes and tithes, they make money from me. Am I a drain on Luna Arcanum in CoH? They are making prestige off of me. When I am soloing, I am still contributing. I'm not always on the team, but I am engaged in teamwork. Maybe not as obviously as when I am in a group, but it is still happening.

If I don't participate with the group as a whole, I do not expect to get the same preference. A raid or taskforce won't ever hinge on my showing up, nor can I expect them to hold a spot for me when others want to go unless I have given the group time in return. Many of the new soloers do not expect such. They are not asking you to bring them on every raid and leave them alone at all other times. If they are, their solo playstle has nothing to do with them being a leech.

Sometimes, even in the most solitary of moods, people like to know others are near and can be reached if necessary. You can solo and be in an MMO. Just don't take it too far one way or the other. Warhammer, for me, had lost its appeal when I was always soloing. If you have soloers in the guild, maybe they just need a friendly hand extended. If you always run in groups, keep in mind that's not for everyone. One former friend in City of Heroes physically could not cope with 8 man teams and would sooner leave than put themselves through strain and no one would say that they were wrong to.

Finally on the grouping side of the fence.. if you never put yourself outside your guild or outside yourself, consider this. You are missing an experience and you may not make friends you otherwise could. My life is richer, online and off, for having pugged and talked to groups.
There is no one ideal playstyle for an MMO in the same way that there is no one ideal MMO for all us online players. If there was, we'd all be raiding tonight, some in groups, some by themselves and some just sitting by and watching us do it.