Sure it would add a ton of new costs and headaches (takedowns, etc), but don't you have to have a plan for this if you're Yishan? Imgur hasn't exactly been subtle about adding reddit-like features (comments, comment ranking, categories, etc)..
New free image hosting services pop up every few months to try to take imgur down as the king of Reddit. So far, they've been unable to maintain any leads gained, but if imgur screws with Reddit they will be replaced in a heartbeat.
To keep traffic "on premises", ie thwart competition. Just look at imgur: now it's sort of a micro reddit, with its own commenting system, categories, and so on.
So you're a site with a major feature that (a) drives publishers to another site, and (b) drives viewers to the same site, even though (c) the content was created for your site. And now (d) that site is adding some of your core features. I guess I can't see how that isn't a blindingly obvious concern if you're running reddit.
Reddit gets the traffic, imgur pays for the bandwidth and compliance.
For what little (nothing?) it is worth, it upsets me that this pattern is repeated over and over and over... for once I'd like to see a startup grow organically over time, never forgetting their roots, not being worth $4 billion after a year of being in business and just acting like a good, solid, mature company that grows into something valuable over a decade.
These overnight-billion-dollar dice rolls are getting exhausting and while really addictive and interesting, they just suck the air out of the room.
http://www.reddit.com/about/team/
Not sure if those are all full time roles though.
But they are always shooting down anyone who dares to use their data and present it in a more useful manner.
In particular they're totally screwing up some areas and ignoring complaints.
The Denver/Boulder area of Colorado has multiple overlapping sites that cover an area smaller than that of the Bay Area, which has one all-encompassing site. The result is that it's really hard to figure out where to look for listings -- or where to post listings.
What we need is combined area site like the Bay Area has, that lets you restrict to certain sub-regions for some searches (apartments, say) and broader regions for others (antiques?).