I'm kinda torn on this, and I guess the reason is that in my mind there are two separate issues here - DLC meaning add-on costumes, weapons, and even so-called "story missions" that are little more than 10-15 minute diversions that play no real role in the game. Then there is DLC as in legitimate expansions to the game - examples of this would be the Borderlands expansions, Minerva's Den for Bioshock 2, the Fallout expansions, etc.
The first kind are money grabs, true, but usually they don't matter at all. Like someone else said, most games these days are so full of side content that you'd never miss a random mission, gun, whatever. Heck, if the preorder DLC I get with games is store exclusive or sought after I usually sell it, because some ppl will pay what I consider to be crazy amounts of money for the crap. It's pointless. But I usually don't begrudge the companies that do this either, because gaming budgets are so expensive these days that if there are people willing to pay for the pointless digital doo-dads, why not sell it to them? I do admit that some companies get TOO greedy, and ironically most of these are Japanese companies. I was telling my wife this past weekend that I would totally buy the moogle costume for Lightning in Lightning Returns, but S-E is asking $4 for it which is crazy IMO. I'd give them a buck for it.
The other legitimate DLC is usually released on disk at some point in a "Game of the Year" or "Complete" edition. So if it turns out to be content or a game I really like, I'll trade off & buy that version when it comes out to have it all on disk. Or sometimes if it's a game I want to play but am not dying to play day 1 I'll just wait for that version to hit (Borderlands: The Pre-Sequel is a good example of this, tho I also fully anticipated them porting that to current gen so that was part of my reasoning as well).
So I think the other more important issue is actually a third one that has been mentioned a couple of times in this thread - not DLC, but patches. When a company releases a game that is severely broken on disk so that you basically have to patch it to play it, those are the games I worry about in the future. And those are the games we should be boycotting, which is why I haven't picked up Unity yet. I'll grab it used, or *maybe* new if the Collector's Edition gets clearanced down cheap enough. But I won't be paying a price that will benefit Ubi Soft on that one.