I don't think you actually can come back. Two and a half years ago, I thought maybe I could. But I haven't. At the time, I was halfway through my undergraduate studies, so of course I didn't then. But now I'm 30 years old, I've graduated, and I'm looking around...and I just don't see anything of the place I used to know. I mean, it looks the same, I am fiercely clinging to my Jukka, but there's review nodes now, and poetry, and...it's just not what it used to be, I think.
I left because I realized there was no mission satisfaction for me anymore. I had initially thought it was possible for E2 to change the world. It started before Wikipedia, and I thought it would become what Wikipedia is now. I like the ownership of individual content like E2 has, but apparently the merged community creations are what make Wikipedia - or any online encyclopedia - truly great. (Remember h2g2? Yeah, me neither.) So E2 never made it big like Wikipedia, and in early 2006 I shifted my not-so-considerable talents over there. Of course, I don't do much there, because I still prefer personal ownership of content...but when I write stuff, I guess I write it there.
I will always have a fond spot for E2. I remember when it was a huge part of my life. But those years are gone. Hang tough, E2. I hope you find an owner soon. I'd like to leave my account kind of in situ in case I decide to come back for real someday. Hugs for all.