Bonuses instead of raises

Today's WP has a story about how more and more companies are using bonuses instead of pay raises to reward high-performing employees.  A survey for Aon Hewitt found that companies had reserved 15% of payroll for bonuses as opposed to 3% for raises.  From an employer perspective, this practice allows companies to target rewards and avoid getting locked into long-lasting salary commitments. Employers also think that performance-based rewards get employees to focus on behaviors that boost the bottom line.  

On the employee side, a bonus is better than nothing.  But companies are less likely to provide bonuses in years when financial performance is lackluster, so employees would do well not to count on bonuses year in and year out.  

Side thought: Companies rarely, if ever, cut salaries.  Why is this practice considered taboo?  Prices for everything else go up and down as the market demands, e.g., gasoline, groceries, housing.  Will we soon get to a point where wages and salaries can go down as well as up?