The other source again from PG, that I can infer as not doing too many things/working on too many ideas is: http://www.paulgraham.com/startupmistakes.html
Read the #18 (A Half-hearted attempt)
I am sure there are folks who have juggled more than one Idea and succeeded in all of them. Also, I think the relevance of these posts also probably make sense to someone starting out early (like say during building the product/company) and probably not for someone who already is working on established companies (like in Jack's case). IF you see Jack in fact moved out of twitter to completely focus on Square and only when it had hit the road running, did he embark back on twitter.
The other source again from PG, that I can infer as not doing too many things/working on too many ideas is: http://www.paulgraham.com/startupmistakes.html Read the #18 (A Half-hearted attempt)
I am sure there are folks who have juggled more than one Idea and succeeded in all of them. Also, I think the relevance of these posts also probably make sense to someone starting out early (like say during building the product/company) and probably not for someone who already is working on established companies (like in Jack's case). IF you see Jack in fact moved out of twitter to completely focus on Square and only when it had hit the road running, did he embark back on twitter.