It is one of those in the overall scheme of things, this was not the right thing to do, overall. This specific case, seems like everything is working out well enough.
It could be argued that this statement is incorrect in the sense that had casascius not massly propagated this issue throughout all intertubes connecting all bitcoiners (in this case via emails only), then this would not have been as noticed as it has been and the following may have had continued:
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http://casascius.net/ still existing as phishing site and NOT redirecting to
https://casascius.com/ and providing opportunity for additional fraudulent revenue (note that the .net domain is still managed by the phisher and at any time could cease redirecting to .com domain)
Perhaps the concern is more about the content of the mass email than the intent of the mass email. This may be more accurately recognized in consideration of my similar efforts in which I emailed ALL THE HACKERSPACES and messaged ALL THEIR IRC CHANS asking a simple/short question or providing a simple short statement suggestive/asking if they've heard about the european bitcoin conference next month. Most of the hackerspaces were appreciative of my spreading awareness and even offered to relay to mailing lists, etc. and were not defensive or expressing of dissatisfaction for such unsolicited technology-related informations/news. Also, similarly my effort towards
Bitcoin Around the World in which I unsolicitedly messaged all non-usian IRCers with short message similar to "hiya. have you noticed #bitcoin-xx? that is all ^_^ *waves*" were mostly accepted/appreciated since many of the individuals didn't realize there were others from their country or even forums, mining pools, exchanges, etc for their country. (note: there were a few that backlashed/raged* similarly as to this experience here, but they were obnoxious minority)
Let's evaluate what casascius's mistakes were:
Sorry to be sending e-mail to the Mt.Gox leak list. (unnecessary/obnoxious)
Please be advised that a recent e-mail purporting to be from me regarding Casascius Physical
Bitcoins is fake and leads to a phishing site. Don't give out your info unless you're sure you're
at the right place. (maybe okay, but perhaps could be stated more simply)
The real Casascius Physical Bitcoins website is at https://www.casascius.com. (This is the controversial part*)
If you do not know how to verify my PGP signature, consider looking me up on the forums to make
sure you have the right address and are not being phished. (unsure if this is acceptable or not)
Sorry for the hassle and the inconvenience, but I suppose this was going to happen sooner or later. (also unsure)
*controversial part: Is it better to link to the phishing site only? the phishing site and the original/real site? no links at all? any reference to which site is the phishing site? any reference to which is the real site? is it acceptable to indicate which operation/site is being phished?
Also, the smallest of concerns/issues liek these...
small/family business: FUUUUUUUUUU, my business's reputation is declining...
corporation: *ignore until it costs more to ignore than to not ignore*