I had no problem losing 2lbs/week until I hit the upper "normal" range of BMI for me at 169-162lbs. Since then I've only lost about 1lb/week instead of 2lbs. But that's still good progress that I'm happy with.
Basically, its really easy to drop pounds like mad in the beginning, but the closer you get to your perfect weight, the slower you will lose pounds. However, the closer you are to goal weight, the more each pound matters. I used to have to lose 15-20lbs before I would see a difference in my waistline. Now I drop only 5lbs or less and there's an immediate difference!
Paper Towel analogy
P.S. I'm 23 and I think age plays a part in how fast you can lose weight as well. Younger bodies adapt to weight changes faster.
Start date: Sept. 2013 at 216lbs
End date: whatever weight gives me a flat stomach. I'm apple-shaped.
216: size 16 jeans, XL shirts
185: size 14
170: size 12, L shirts
165: size 10
159: size 8, M shirts
150: size 6
140: size 4 (can't find anything smaller in womens)
130: size 5 (juniors)
*Note: these are the sizes I usually fit when I try on things at Walmart/Kohls/JCPenny/Sears etc. ALL of them practice vanity sizing.