What are the risks involved with rebreather diving?

There are a number of risks associated with rebreather diving.  Essentially, these risks are related to the rebreather itself and the quality and proper functioning of the equipment, rather than any issue with rebreather techniques.  Rebreather divers are more susceptible to any and all risks faced by divers in general.  These include hypoxia; oxygen toxicity; carbon dioxide poisoning; and disorientation, panic, headache, and hyperventilation due to excess carbon dioxide.  Divers must also continuously breathe in and out and must do away with any breath holding practices they have learned previously.  Finally, if any water comes into contact with the soda lime in the rebreather, a caustic cocktail will result, which can be detected by a chalky taste in the mouth.  Overall, rebreathers are more expensive, have more complicated maintenance and repair, and have fewer failsafes.