I have two Berettas, both DAO Centurions, one in 9mm and the other in 40S&W. The DAO Centurion happens to be my favorite self defense pistol as I liken it to a revolver with a great trigger job, more capacity, very accurate and just as reliable. This is my take on why they slid down the popularity scale:
1. Too many people knew too little about the military slide failures and bought into the idea that it would happen to them.
2. Too much exposure in Hollywood; people by nature want the latest and greatest and Beretta became old news.
3. It is a big gun, no doubt about it, and the desire for more compact pistols took precedent, particularly after the capacity ban took effect, Beretta failed to meet that demand.
4. Finally, I believe that Beretta's marketing leaves a lot to be desired. Obviously this is just one person's opinion, mine, but I don't feel that they met the competition of Glock and Sig effectively at all. The Cougar was in the same size class as the Glock 19/23 and Sig 229, both very good guns, and a very good gun in its own right. Beretta just wasn't able to find the right hook or niche at this time and took a step backwards.