Once I saw the Portal 2 trailers, something bothered me. Portal 2 uses a few gels to aid in puzzles.  Repulsion Gel & Propulsion Gel, have so far been revealed.
This reminded me of a game I saw on 4/7/2009. That is the day that on the video program CO-OP, had their "Indie Games Special" where they showed off several indie games and their devs. Well, if you watch that video, you will see a game called. TAG: the power of paint.  
 
If you have played the game or seen that episode of CO-OP, you will notice that TAG uses gels or "paint" to apply different effects to the ground. Red for speed. Green for jumps.  Blue to stick to objects.  This just seems alittle strange. 
 
If you would like to read more about "The Power of Paint" go to  https://www.digipen.edu/studentprojects/tag/  (The website given in the episode has since shutdown) And if you'd like to see the Indie Games Special you can download it on itumes or, go here  http://revision3.com/coop/feed/quicktime-high-definition/.
 
Does anyone else find this strange?

 

They actually recruited all of these individuals because of their ideas in TAG.

Valve bought or hired them was what I heard same as the first Portal and its portals. 
 
EDIT: Yeah what the other guy said.

There's already a thread about this but as has been said it was the folks at DigiPen who originally came up with the whole Portal mechanic and Valve hired them to work on Portal. Now they're hiring the DigiPen folks behind TAG to work on that mechanic for Portal 2. I'm glad that Valve have been able to see the potential in the work of people who would have otherwise only been small-time designers/programmers and have brought that work to a larger audience.

Ah, I just came from posting links in the trailer comments to hopefully remind people of this very thing. I checked the same CO-OP episode as well. :) 
I'm surprised that in all your link researching the articles on the Digipen team being hired by Valve didn't come up.
And no it's not that strange. Narbacular Drop was the student project that begot the first Portal.  I can imagine that Portal 3 will bring in ideas from another crop of students.

Yeah, and I read this on another thread yesterday. So, I download and installed tag, and it's pretty sweet. It's going to work well in Portal 2.