Creating vlans at the core layer ?

CCIE_2011

Hi guys ..... I already did asked this Question in CCNP section but they say it need experts to answer this. here you go guys.
What are the pros and cons of creating VLans at the core layer in cisco hierarchal design??
Keeping the in the distro layer isn't just better ?

CCIE-4-HIRE

There are a lot of reasons to do it this way and not to really. I have had the pleasure of doing it both ways. But in general, I will tell you I have preference. If you can tell me more then I can give you more of a real opinion in the matter.