Not a lawyer, but as I understand it, trademarks often cover only specific market categories. That is, someone can in some cases use a trademark in a market category that the original trademark owner does not operate (e.g. Company1 using BrandA sells only consumer electronics, some Company2 can actually later use BrandA to sell baby diapers). As long as BrandA isn't sufficiently famous and there is no risk of confusion or brand dilution, then Company2 isn't necessarily going to get in trouble.

Of course, determining where the line gets drawn probably isn't always a matter of checking off items in some checklist (gray areas, etc.). Nevertheless, in the case of Newegg's Shell Shocker deals, it doesn't seem to me like it overlaps with this site's intent (vulnerability testing). Only overlap I see is that it's something that's operated over the Internet. Would be far-fetched to say that this site is capitalizing on Newegg's brand goodwill to... get people to test for server/machine vulnerabilities.

Also... "It is not necessary for a trademark owner to take enforcement action against all infringement if it can be shown that the owner perceived the infringement to be minor and inconsequential. This is designed to prevent owners from continually being tied up in litigation for fear of cancellation."[1] So just because Newegg has a trademark doesn't mean it immediately and invariably has an obligation to enforce it at the threat of losing it.

[1] http://en.wikipedia.org/wiki/Trademark#Maintaining_rights