I've read that Encarta represented the first shoe to drop for EB; it could not easily adapt to that technology shift. Now, with the benefit of hindsight this does not seem as though it would have been such a big change.
The major paradigm shift lay in the enabling of two-way online communications. The passive consumer could now also become a content producer. This wasn't quite what ISP's had hoped for in an asymmetrical technology that assumed that the public would want to download far more than they would upload. Their model also presumed that they would profit from also providing the content.
I'm not sure this changes my point. If Britannica had adapted to the proliferation of personal computing and portable media by releasing a comprehensive, easy-to-use and widely advertised electronic edition before Microsoft managed to release Encarta, they may have remained on top into the 21st century. Similarly, if they had jumped on the Wiki bandwagon a little later, they may have further adapted and remained on top for several more decades.
One should not presume that any specific technology will be the one that leads to the big steps forward.
Again, this was not my point. We should not invest in few technologies and hope they win out, we should spread our bets. We should adopt and adapt to new technologies as soon as they appear. We shouldn't be afraid to change; Britannica were and they are dead.