Sometimes I scroll down for a while, and sometimes I leave Twitter open and check new tweets as they come in. But following a couple of hundred people means most tweets are part of that magic 7 for less than a minute - that's not a lot of time to catch someone's attention enough for them to click through to an article, reply to your question, even retweet.
Some more stats from Smashing Mag (or another test from someone with a large following) would be useful. Counting hashtags and testing for quality replies misses those who reply without the hashtag, and overlooks other engagement metrics.
Good to see the dilemma highlighted with some data though.