No, you probably didn't. There was a site posted around here recently where an EE dissected switching PSUs from Apple, some other phone co.s, and some cheap knock-offs. There are appreciable differences in the design and component selection regarding things like filtering caps, space between HV and LV sections, transformer isolation and current capacity, and other things that dictate quality of output, and more importantly, user and property safety. Don't skimp. You don't have to pay the Apple tax necessarily, but at least get one with full regulatory certifications. Although the Apple ones were of particularly high quality, so it may be worth it.
I consider this doubly necessary when the PSU isn't driving a well-engineered and tested load.
Be safe guys - PSUs are no joke.