Interesting to note that Spring sees a yearly surge in interest between February and April. Are you sure you cleaned your data correctly, or did you just search by keyword?
It's interesting how Django manages to get good mention on HN. But the fact is, there are very few job opportunities for Django developers compared to, say, Rails developers. Even on the supply side, its difficult to find Django developers for startups.
Rails seems an ideal language for startups, but I was still surprised to see how highly it plays on HackerNews.<p>Lot's of great quotes in this article from earlier this week about why startups in Boston are using Rails:<p><a href="http://bostinnovation.com/2011/03/22/boston-companies-using-ruby-on-rails/" rel="nofollow">http://bostinnovation.com/2011/03/22/boston-companies-using-...</a>
More data:<p><a href="http://news.ycombinator.com/item?id=1843083" rel="nofollow">http://news.ycombinator.com/item?id=1843083</a><p><a href="http://news.ycombinator.com/item?id=750142" rel="nofollow">http://news.ycombinator.com/item?id=750142</a><p>etc. You can search on google with "site:news.ycombinator.com" as a prefix and get useful results on pretty much anything startup-related.
I think the languages that's going to win is the one providing the best value and the easy adoption. I tend to go for nodejs. How many times a language is mentioned does not necessarily reflect its power or its capabilities.
Although Spring and Rails do similar things I think they serve two different roles. A more accurate comparison would be something like the Play! Framework, which would barely register (unfortunately)