It's the constant pressure from VC's for better monetization. One of the features being discussed on the thread over on Reddit that is planned to be introduced is a location-based front page. This will make targeted ads by location an easier product for Reddit to sell and mine data from.
And many many users will leave, as they did with Digg. It's too large and lowest common denominator already, and a major redesign will be the impetus for a brain drain as all users will have a shared gripe. HN is a very likely spillover target, and already is for a lot of the programmer focused discussion that used to be Reddits core user base. I've watched so many communities die from monetization, the cycle really writes itself.
Eventually even HN will get too bloated and need to fracture.
I definitely think there is a risk. However, reddit is much larger now than Digg was then. And reddit existed as a clear alternative to Digg at the time of the redesign.
I think there's a very real risk of a redesign going wrong, but it may be large enough and better enough than alternatives to weather the storm.
"Better enough" is a funny thing when it comes to redesigns, because all the previous routes to value that are ingrained into your brain are now gone, or look funny/different. Thats why I predict a brain drain as people pick up and realize it really doesn't do much for them anymore.
Necessary or not squeezing more profit out of the site is going to drive many people away I saw it we all saw it with digg and slashdot.
I can even hear "Let's try for 5% growth next year!"
Then if there is no growth the cuts begin from the bottom up to protect the executives. Be warned! First they will come for the lunchroom coffee creamers...
