Paste tool crops transparent parts of pasted image thus modifying it without asking or telling user about it. If it's what some people would want there should be at least preference for turning auto-cropping off.

Why it's bad? Because if I want to position a lot of images with transparent borders one over another in layers auto-cropping is unacceptable. My current workaround is to place black pixels in all corners of all copied/pasted images but that makes editing much more problematic.