It's been interesting that sites have reported actresses up for the part of the 'love interest' and never specified which character. Yeah Emma was a natural blond but someone suggested that she dye her hair for a film and she liked it so much that she's kept it that way, can't remember what movie it was for. Read this just a few days ago.
Actually Mary Jane and Liz were classmates of Peter's in "Ultimate Spider-Man" Gwen was introduced in Ultimate Spider-Man #14 (the beginning of the third arc). It's going to be interesting to see if MJ even appears (which I'm starting to doubt right now) and what interpretation of Gwen we see in "Spider-Man". I wouldn't mind if they use "Amazing Spider-Man" for the title.