The internet gives a medium via which us fanatics / obsessives / anoraks can interact. So Bowie's work can be meticulously discussed and picked over at previously impossible levels. Back in the eighties, where would you have gone if you wanted to discuss the merits of Eno's oblique strategies on the Berlin trilogy?
Bowie's immortality or presence over modern culture isn't thanks to the internet, if anything it's been detrimental to the quality of his output. When Bowie went online his work went downhill: he got a fan to write lyrics for the relatively lame Hours, he re-recorded his 60's songs, he planned a Ziggy 2002 project. It was when he got off the net and into a remote studio built in to the side of a mountain that he found his voice again.
Bowie's 'immortality' is down to the music he's created which has influenced subsequent artists. The year long
NME poll of contemporary bands from '99-'00 which found Bowie to be the most influential artist of all time is evidence of this.