The idea that every client has to ping a server to get a text file just to see if the player gets a special cape is pretty weak.
Note that GregTech did add Capes before RichardG did. But I added the online Variant of mine after him, as I had (and still have) a hardcoded List back then. Now I have an Online List running since a while, and I even provided a Config to turn any Online-Checks off, as Internet sometimes lags terribly when connecting to Dropbox or similar Sites (especially for chinese people as I found out). Some Sites are indeed so terrible, that Minecraft freezes for me at the MOJANG Screen, so that I have to disconnect from the Internet while loading Minecraft, not because my Internet is crappy (It's in fact faster than most Download-Servers), but because some of these Servers are not responding, and Minecraft just waits it out forever and ever and ever and ever and so on.
Though it could be possible that RichardG wants to take over the world...
He will fail at my Space Station, so you don't need to worry about that. I would more worry about me having a Space Station.
2. Java is an EXTREMELY easy-to-hack coding system. People still on 1.7.0_11 (or something like that) or lower can be hacked if they're playing MC.
But you can only hack MC-related things (Username and Passwords too), not other personal things.
It matters to some people that have terrible internet, and instead of waiting for an update check they can disable, they MUST wait through a cape check.
As I said, its not your Internet which makes it slow. It's the Internet of these partially crappy Servers some Devs chose for their Lists. I think SirSengirs checks for a Changelog are terrible at my own location (for example) as it began to refuse to start, when Forestry was updated. But I shouldnt be the one talking, as my Dropbox based List is terrible in China (but configurable).