It's not really responsible to encourage people to click on links that purport to tell you if you're affected by this or any other breach. There are dozens of such links tweeting around that are probably phishing scams.
Given the nature of this breach -- someone used a now well-known API to poll the database millions of times -- we should probably simply assume that the entire Snapchat database has been accessed (even if only 4.6M records have been posted). If you are not in the 4.6M then you annot be sure you're safe. And what are people going to do in any event? Change their phone number? It's too late! The grave thing about breached phone numbers is that they are going to be used by organised criminals as indices to link multiple data sets; the phone number in itself is almost irrelevant. Nobody should ever give their phone number to a social site.
The long term personal ramifications could be card fraud or identity takeover. The only ting people can do if they're Snapchat users is to stay vigilant, closely watch their card statements, maybe subscribe to a credit watch service ... all of which is good advice these days regardless.
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