Very sad news. Mark Evanier has a touching eulogy at his site.
I didn't know Steve Gerber, but I enjoyed his work, especially his Man-Thing comics from the 1970s. I re-purchased the whole run a couple of years ago on ebay and was slowly (too slowly, alas) working my way through them.
If you're so inclined, you can read Steve's blog, which chronicled his struggle with pulmonary fibrosis, along with happier subjects like his recent comics work on DC's Dr. Fate.
It's a good example of how you may not know someone, but you learn about his life and even feel a personal connection to him, through blogging.
Definitely a 21st century experience.