Thinking in Generic

Hi Folks,
Can't wait to hear more about Generics and Templates fine-very-not-butchery feature of modern languages?
Well, sorry to disappoint you but you've got the wrong track (I'm not such expert of that, btw, raise their hand those who created their own class using generics in the last week).
I'm gonna talk instead of how people (even honest butchers like us) can try to be as generic as possible while designing their application.
I wanna introduce my personal thumb rule:
Don't make any assumption if noone will risk his goddamn neck without it.
It may sound like an easy one, but in my experience this is, in the 80% of bad designs I've seen, the main root cause.
Sometimes I've been asking around questions like:

• "Why is that field of a so specific type ?"
• "Why you DON'T need to have such information on your class?"
• "Why these two classes do not have a common ancestor?"
• "Why these properties do not belong to a super?"

Problem arises when the answer is: "I don't need that in my case" i.e., "I can assume this in my case".
Well, even a butcher like me could still ask you WHY?
OK, I've got it.
YOU think that you can make that assumption but, even if it's true (so far), why should you?
What is the catch? Saving manicure to your hands or 30 minutes from your work-clocking?
I've got it, you are saving those 30 minutes to beat Lou on Guitar Hero (yes I know you are a geek).
But, if you can't find any other reason to make those assumptions, you should just make to yourself (and to those who'll handle your design after you) a favour.
Don't make them.
And this is the reason why: there are very good chances in the air that you would be bitching yourself within a month (or that your colleagues will be bitching you) for that, believe me.
It's just an honest advice from a butcher, you don't think it's worthless right?
That's all for today, I've gotta finish writing some ugly (very butchery indeed) nested loops...