I followed the wikilink you supplied and landed at the homepage of the 80 plus certification where I found a datasheet of the 350 W PSU that popped.
http://www.plugloadsolutions.com/psu_reports/XILENCE_XP350.(12)G_ECOS%201752.1_350W_Report.pdfWhen I look at the input-output diagramme it clearly states that it needs about 400 W to supply 320 W.
Also in the wiki it says
In some instances a reseller has claimed a higher wattage than the supply can deliver - in which case the reseller's supply would not meet 80 PLUS requirements.[4] The 80 PLUS web site has a list of all certified supplies, so it is possible to confirm that a supply really meets the requirements
Which sounds to me like every 80 PLUS cvertified PSU should be able to deliver the wattage that is written on its packaging, right? So my 350 W PSU should supply 350 W without blowing.