Pingdom has blogged about their research which seems to indicate that Pinterest has overtaken Tumblr in the US market.
Both Tumblr and Pinterest have been incredible popular on the web. Tumblr offers micro-blogging capabilities while Pinterest is largely used to share cool stuff from around the web.
The two services are not comparable but both are major players in the social services market and traffic comparisons are bound to happen.
Pingdom report stated that Pinterest is massively popular in the US and Canadian markets. Tumblr on the other hand has a global fanbase. The report further said:
Pinterest has taken the United States by storm. The rest of the world may still not have caught on, but it’s worth noting that this is how many of today’s social networks got started. I.e. first they grew in North America, then a gradual expansion into the rest of the world. Facebook did this. Twitter did this. And we bet Tumblr did, too. Next up, Pinterest?