In his first column, he describes the major technological trends that are driving grassroots media, outlining the key developments of blogging, podcasting, wikis and mash-ups.
Mr Gillmor, who coined the mantra "journalism is a conversation, not a lecture", writes: "For my part, the most exciting aspect of this change is in the emerging conversation. Bottom-up media tools are conversational in nature, even though they can be used in a top-down mode.
"It is more accurate, actually, to think of these tools as 'edge-in', deployed and used from the edges of networks."
BBC readers were quick to respond to Mr Gillmor's description of the democratisation of the media.
"Democratic it is maybe, but the big issue is reliability," said 'Adam Morrissey of Sydney'.
"As readers, we've become used to trusting at least some media outlets - we generally assume that a journalist working for a genuine news outlet is trained and has conducted proper research. You can't make that assumption with net content."
'Disgusted of Mitcham' defended the format of blogging because it allows readers to write back.
"That provides at least some protection against writing pure garbage. Compare this with newspapers, which get to choose which of their readers' letters to publish, and consequently get away with writing utter rubbish most of the time with no public corrections."
Criticism of traditional media was a common theme among the comments; 'Alex Kiss of Manchester' said citizen media has fed on public mistrust.
"The gulf between the professionals and ordinary people is now glaring. It is now the amateurs who are asking the hard, insightful questions, refusing to be brushed off with evasions and actually maintaining the principals of journalism which the papers and others have cast aside in their quest for market share," he commented.
"This sort of public involvement would not be half so widespread if the traditional media were doing the responsible, challenging, neutral and representative job we expect of them."
Dan Gillmor's future columns will include copyright and privacy, and how media businesses are experimenting with these new, interactive publishing tools.
He recently wrote about the problems and discoveries of his experimental citizen media site Bayosphere. Designed as a collaborative, participatory journalism project for the San Francisco area, the project stalled because it did not have enough contributors or a rigid enough framework. Despite the problems, Mr Gillmor was widely praised for his transparent and open explanation.
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