Maybe it’s because those two icons looks so similar? Or perhaps people want to “spread the news”?
Whatever it is, the scenario is always the same: Somebody sends around an email to a group of people, containing perhaps an invitation to a conference, a request, a question or something similar. And of course, all recipients are listed in plain sight in the “to” field. So events follow their their natural c(o)urse: a couple of minutes later, your inbox becomes flooded with a lot of “Sorry, don’t know”, “Oh yes, please!”, “Sorry, I won’t be able to attend” or “Would really LOVE to come, but my cat is sick…” or similar answers of obvious importance to all the 50+ people who were receiving the initial question…
I just came back from vacation, and a rough estimate leaves me with around 200 of such mails. And unfortunately, no spamfilter can handle them.
Please: it’s just a small difference, the “reply” and “reply all” icons really look alike. But it matters. A confirmation or decline might certainly be important to the initial sender – but often that’s it.
And if you’re sending around these types of circulars to a large group, why not considering to use the “bcc” field instead? So that people don’t get tempted.
Thomas