I don't agree that Twitter is a very low cost-to-switch environment. Its value only comes with scale - I think it would be difficult for non HN users of Twitter to see enough value to make a switch, at least, not without something new or quite compelling...
I had to be 6 or 7 - BASIC, then Assembler, on a Timex Sinclair 1000 - 2K of memory and audio tape storage - moved up to the 2000, then the Coleco Adam, and finally an 8086 I assembled with my father....