The scale of Facebook resources (or Google's for example) makes it easy to clone pretty much any product that fundamentally enables two or more users to interact. At a certain scale of resources, most software products are easy to clone because rarely are they based on some fundamentally new/patentable/distinguished technology. What's hard to clone is the interaction, and it's for that reason that this probably wont make much difference to Snapchat. I've only used Snapchat a couple of times in the past and the type of interaction it enables doesn't relate to the way I think of Facebook at all (and I suspect this will be true for most Snapchat users). Ultimately, almost any app, at infancy, is easy to clone - Facebook could have cloned pinterest/twitter/path/quora etc (and at times it tried), but that's not what killed them/would kill them. If they do die, it will more likely be from not tending to their community & executing on their vision. Frankly having Facebook clone your product is probably worth its weight in press alone.