A few weeks back, I laid out my aversion to Facebook and the like.
When I updated the site code a bit to add tags, I considered whether to add all the now-standard bullshit Like/+1/Pin/Reddit/StumbleUpon/Digg (Wait, Digg? That's Still a Thing?) buttons to the bottom of my posts. They'd probably get more exposure that way. And hell, maybe someday, if I'm actually concerned about getting exposure instead of, say, people stumbling on my site randomly while doing a search for "did stan lee bone at jack kirby's wife", I'll bite the bullet and stick a linkbar down there. But for now, I'm perfectly happy with my uncluttered little niche site. (Reminder: this site's title is meant as irony.)
Now, the thing is, upvoting actually does have positive applications. Not just in terms of exposure, but it's a great way to organize a comments section, provided it's implemented as it is on Slashdot or Reddit: popular posts become more prominent, while the trolls get drowned out.
Of course, this has the potential to result in mob-rule stupidity. That's why Slashdot doesn't allow just anybody to upvote comments; certain users are selected as moderators (and other users are selected as meta-moderators to help ensure that the moderators reflect the community). Slashdot's not perfect, but it uses a very effective model for its comments section. (On the other hand, if you put the power in the hands of too few people, you end up with a situation like Digg -- which I quit reading some years back precisely because I thought the voting had fallen to the lowest common denominator, but which as it turns out was being tightly controlled by a small and select group of morons.)
Course, that's not what the Like/+1/Karma/whatever button is typically used for. Typically it's purely masturbatory -- it doesn't affect which posts are more or less prominent, it just functions as a scorecard. The people clicking Thumbs-Up or -Down get to stroke their own egos and the ego of the poster (and it doesn't matter which -- do you really think someone who's got a shit-ton of thumbs-down clicks is any less satisfied than someone who got a bunch of thumbs-up? Because here's the thing: if somebody's got dozens of thumbs-downs, that is exactly what he was trying to get.). It's also a very rudimentary form of gaming, of the sort Ian Bogost parodied in Cow Clicker.
I'll say one thing for it: it at least serves as a substitute for people writing banal little one-word praise posts ("Seconded!", "Yes!", "Like!", "This!"). I'd rather see a "+100" next to somebody's comment than 100 one-line replies.
That said, I'd rather people actually, you know, find intelligent things to say.