Like the concept and if you work on the feedback, then you are onto something and I think your competition ATM is Google+(haven't used G+ yet). Get a co-founder and a strategy. Your "Add tag" should read "Press Tab to add tag" or similar. I should be able to comment with my OL(yeah, Overlap) acc since i have one. Nice design, but needs more work(you have set a high par,run with it). Breath deep and give us something great.Good Luck