Even if there was no specific agreement, Lifehacker abides by the terms of the license you place your content under when posting it to Stack Exchange sites. From here, which is linked to from every SE page's footer:
- Subscriber Content
You agree that all Subscriber Content that You contribute to the Network is perpetually and irrevocably licensed to Stack Exchange under the Creative Commons Attribution Share Alike license. You grant Stack Exchange the perpetual and irrevocable right and license to use, copy, cache, publish, display, distribute, modify, create derivative works and store such Subscriber Content and to allow others to do so in any medium now known or hereinafter developed (“Content License”) in order to provide the Services, even if such Subscriber Content has been contributed and subsequently removed by You. [...]
(emphasis mine)
All your contributions are licensed as CC Attribution-Share Alike, and the Lifehacker post follows the rules (linked in the footer copyright statement) for attribution as specified by SE (relevant for you: they're linking to the original post and your user profile on SU).
There appears to be some disagreement (see comments on those posts) whether the way the terms of use are presented (or not) means they're enforceable, but that's only if you're really determined and willing to pay for a lawyer.
guys
in New York are churning the bigs bucks out of all this.. I suppose I have something out of it too..