It used to be that we found out the names of products when companies announced them. Though that's still the case now, the rise of the Internet has allowed us to unofficially dub unannounced products before any confirmation is even received that a product is in development. The Nexus 5, Xbox 720, Android Key Lime Pie ... even the Lumia 928 moniker was never official until today, May 10.
It's possible we've become better at predicting these things, or that the next name is fairly obvious. Considering, though, that Nokia's entire numbering system for its phones makes no sense whatsoever (Lumia 928, 920, and the rumored 925??), the Internet may have simply made it easier to get leaked information out to the public.
The Xbox 720, for example, seems like a logical enough leap from the Xbox 360... even if the name doesn't actually sound very good. After all, if Microsoft made one 360-degree turn from the first console, why won't they do it again?! Microsoft hasn't commented on its console at all, but it's likely that Xbox 720 will actually be called something else. Recent speculation has suggested Xbox "Infinity" or Xbox "Fusion" as possible names, or even simply "Xbox."
Other times, though, when the Internet dubs an unannounced product, it doesn't really make any sense. Like with the rumored Nexus 5. The Nexus 4 was so called because it featured a 4-inch screen, so why dub its successor the Nexus 5? It could be that the Nexus 4 successor clocks in with a 5-inch screen, but many rumors pin the display at 4.5 inches. Perhaps Google is trying to avoid having to deal with the possibility of two digits making things even more confusing (Nexus 4 2? No, thank you.) Some leaked benchmarks even have the Nexus 5 appearing under different names, so who knows what it'll eventually be called.
Even with Android 5.0 Key Lime Pie, Google hasn't confirmed that it's actually going to call the next version of its OS that. At this point, we expect the name to start with a "K," but Google could call it anything. Even the fact that we know Google is taking names in alphabetical order has caused some fun, since artists designing concept art for future phones have even dubbed Android 6.0 "Milkshake," just for yucks, presumably.
So why bother? Some of these names are based in leaks, while others, like Xbox 720, catch on because they offer us easy, recognizable shorthand for writers and consumers to use when talking about future devices they're excited about. After all, the worst that can happen is you simply have to start using a different title when the new Xbox is unveiled.
For us, that's nothing. For those coming up with the titles, the pressure is much heavier. After all, nothing's worse than choosing the name and completely screwing things up. That guy who thought "Wii U" was a good idea? We wouldn't want to be him right now.