I was just marking a student's paper and he used the phrase "tumbleweed effect". I was pretty sure he meant to write "snowball effect", but I googled the phrase just to make sure I wasn't just ignorant of some new turn of phrase.
It turns out my student likely was trying for "snowball effect", but there is some use of the phrase "tumbleweed effect" out there. The most interesting one I found indicates that, in a discussion forum like this one, a poster's Tumbleweed Effect is the percentage of his last 50 new threads that have gone without even a single reply.
Because this forum is still fairly new, most folks probably haven't tried to start 50 new threads, but you could still calculate your TE on the basis of, say, 10 or 20 threads started. If 1 out of your 10 threads has gone without a single reply post, you'd have a TE of 10%. If half of them, 50%, and so on. Before this one, I've started 6 threads on here so far, and one of them had no replies which gives me a TE of 16.7%. If nobody replies to this thread, my TE will spike up to 28.6%! (Although fewer than ten threads is arguably a pretty volatile sample.)
Anyone else here brave enough to click the Posts icon at the bottom of the page and calculate up their Tumbleweed Effect? Anyone here with a jaw-dropping 0%? Anyone with over 50%? 
It turns out my student likely was trying for "snowball effect", but there is some use of the phrase "tumbleweed effect" out there. The most interesting one I found indicates that, in a discussion forum like this one, a poster's Tumbleweed Effect is the percentage of his last 50 new threads that have gone without even a single reply.
Because this forum is still fairly new, most folks probably haven't tried to start 50 new threads, but you could still calculate your TE on the basis of, say, 10 or 20 threads started. If 1 out of your 10 threads has gone without a single reply post, you'd have a TE of 10%. If half of them, 50%, and so on. Before this one, I've started 6 threads on here so far, and one of them had no replies which gives me a TE of 16.7%. If nobody replies to this thread, my TE will spike up to 28.6%! (Although fewer than ten threads is arguably a pretty volatile sample.)

