If you’ve seen the remarkably stupid, yet still oddly entertaining movie, “Beer Fest,” (recently screened for what was surely its target audience, including the Lagerheads and friends, at the Arlington Cinema N Drafthouse), you might think that the beer-pong prowess displayed therein was the product of snappy camera tricks. Any it probably was. But for the real thing (or what appears to be), take a look at this homemade YouTube movie, one of an entire genre to be found there, proving at least one thing: people have wasted a lot of time perfecting a totally useless skill. That is, unless you can make a living as a professional beer ponger… We’ll have to check on that.