OOP - Interraction Between Houses

[rose590]

No: HPFGUIDX 64218

I sincerely apologize if this question has been posed before.  I 
only finished the book this morning and have been unable to wade 
through the mountains of posts in my e-mail.
 
One nagging question I've always had has been reemphasized again 
in OOP.  I had questioned once before about relationships and 
friendships between people of different houses.  For example, Percy
(Gryff) dated Penelope Clearwater (Ravenclaw), and in OOP, Harry 
dated Cho, also of different houses.  Other than Hogsmeade trips, 
shared classes, and the Great Hall, do students of different 
houses have the opportunity to mingle, get together and socialize?

If they do, (which may be the case with inter-house dating going 
on), why then in OOP were the DA so paranoid and think that people 
would get suspicious of them talking with one another (crossing 
between house tables) in the Great Hall.  Or were they so worried 
about being caught that they were just being overly cautious and 
paranoid.
 
I'm sorry I don't have an exact quote on that one, I'm not 
familiar enough with the book yet to be able to find it quickly.

Rose