Shares of Amazon.com (AMZN) are down more than other techs Tuesday, falling $3.96, or 6.35%, to $58.08, after RBC Capital Markets analyst Stephen Ju cut his revenue estimate for this year by a billion dollars — from $20 billion to $19 billion — saying that consumer willingness to spend has deteriorated broadly, based on his check with big-box retailers and e-commerce firms.

“Although Amazon’s product selection is broad enough that we think it will be relatively more shielded, it is certainly not immune,” writes Ju. Ju maintains an “Outperform” rating on the shares, while reducing his target price to $80 from $100, noting that his thesis is still intact about the company, namely that it is gaining share in online commerce at the same time that online commerce is capturing more share of overall consumer spending. However, he’s moving to a “recession scenario,” he writes, which assumes zero growth in retail. Oh, well.

For 2009, Ju’s revenue estimate goes from $24.7 billion in revenue to $21.8 billion. His earnings per share estimates go from $1.89 this year to $1.77, and from $2.58 in ‘09 to $2.16.