There's just been a lot of hype about Ruby On Rails recently, mostly in the past 2 years. And now that a lot of people are using it in production, the problems [of using it] has been magnified. Mostly with deployment and running it in production with lots of users online (can crawl an entire server if you're not careful).
Here's the original rant from Zed Shaw (the master), creator of Mongrel (note though, the picture on the Mongrel website is named Bantay from Cebu). Dreamhost seem to have agreed with him. Now, DHH (the Rails creator himself) is rebutting the posts.
I can smell the pain now (to think Rails is supposedly designed to remove the 'hurt' in programming) -- and a lot of experienced people who have tried Rails and have been disappointed with performance are coming out now -- this is not like how Twitter went sometime ago -- but people are actually supporting their stories with real performance numbers.
Time to move to Merb.