Your question strikes me a flame bait. Nothing in the article says nosql is the only solution, and in fact Wordnik also uses MySQL. But I'll bite. The number o

Your question strikes me a flame bait. Nothing in the article says nosql is the only solution, and in fact Wordnik also uses MySQL. But I'll bite. The number of requests/day might not be as important as what's going on around in and around the requests. Since Mongo lets Wordnik avoid complex joins and supports high volumes of reads and writes at the same time, it works for them. And personally, I know many developers prefer MongoDB's query syntax, and use it instead of MySQL just for that reason, even on small projects or when performance is irrelevant.