For me no face was one of the most interesting characters i have watched in a movie. I think he was lonely, yes, but the whole point of his character was that he was lost, without purpose. He was like a child, lacking a well defined personality, trying to be accepted and loved based on his perception of what others wanted. He was trying to buy affection, so to speak. I think he was a lot like me when i was younger...misguided. Maybe thats why i liked his character so much. I think he may be a metaphor for growing up and realizing what matters most in life. Or maybe i am wrong...

Yes he was just lonely who got attention from Chihiro so he became obsessed with her. Since he was a nobody, he tried to copy those in the bathhouse, hoping Chihiro would like it. I kinda saw it that he was easily corrupted by greed like a sponge absorbing, as he was literally empty. Good thing he was saved – kudos to him for giving the herbal thing, love that scene.

I remember reading a deep analysis on him before, like representation for something in our culture - can't remember where.

Both of the answers above are right on target. One of the subtle themes of Spirited Away is that there are no truly "evil" characters despite appearances. Think of it, every rotten character, from the tyrannical Witch, to her spoiled brat baby, to her greedy underlings, to the creepy spiderlike Boiler Man, each come around to a degree of humanity or even redemption in the end. In every case we realize that these bad characters were the result of corrupting influences. In particular it's the Bath House (greed, luxury, profit) that corrupts everyone while the 1 character who avoids the Bath House--the Witch's twin sister who lives in a modest shack in the country--is free from these influences, and she's the one who sets things on the right track and finally gives No Face a home.

I think No Face is really the central character. If dramas are woven around a protagonist who undergoes a transformation (character arc), then No Face is really the central character who shows this. He starts out as his name implies, completely blank and ambiguous. He follows Sen mostly out of curiosity, mimics her kindness, but then soon mimics the greed & indulgence of the employees at the Bath House, ultimately turning into the worst monster of all. Sen drags him out of there and he returns to his former self (ambiguous observer), until he finally finds the good Twin who gives him a benevolent purpose.

I feel like the core theme of Spirited Away is that lost souls wander everywhere, and whether they land in a good environment or a corrupting one is almost random. Even Haku was a benevolent river spirit before he was lost and became corrupted by greed and commercialism (figuratively: working at the Bath House, literally: being filled and turned into apartments) but we only get the tail end of Haku's story. With No Face we see it from start to finish.