Today we’re announcing the Disavow Links feature in Bing Webmaster Tools. Use the Disavow Links tool to submit page, directory, or domain URLs that may contain links to your site that seem "unnatural" or appear to be from spam or low quality sites. This new feature can be easily found in the Configure Your Site section of the navigation.
Using the Disavow Links tool, you can easily and quickly alert Bing about links you don’t trust. Using the drop-down, you can choose to input signals to us at the page level, a directory level or at a domain level. We’ll note the “type” of location (page, directory or domain) and the date you told us of the action. [bing.com...]
I'll add this... you own webspam isn't good webspam and that which others might develop isn't bad webspam... it's all just the same webspam... you cannot suggest "I'm playing fair" and the evil competitor isn't by using the exact same tactic.
Honestly, submitting a spam report is 100% free and is a far easier and more effective method to harm your competitor - that is exploiting webspam... IMHO people get tunnel vision on the wrong things.
Bing is already much better than google at filtering out garbage links. Quick detour to both WMTs tells me that G counts 4-5 times as many links as B. (My numbers are lower than yours, duh, but I can't imagine the proportions are all that different.) Or 10 times as many, depending on whether you go by the raw number B gives you, or the number of specific links they actually show you. (I do not understand how this works.) Among other things: B, unlike G, appears to grasp that a call to the piwik database is not a link.