I've heard the name and ignored it. But what the hell, let's take a look. Obviously, this website is very popular with some people but if you go to the default page you get this: http://imgur.com/XWdkO8i ...a popup that says "He used Pinterest to start his collection" on top of a blurry background. Who's "He"? Sign up with Facebook? Why? And all this confusion in a popup? Really? The very worst aspect of 1990s web de…
The likely rationale behind the immediate experience of a site that traffics in millions of uniques is that 'the numbers say that the visitors who respond positively to this outweigh the visitors who respond negatively'. In particular, I'd be willing to guess that Pinterest used gendered language in their lead-in because they're in a unique position of having a female user base which outnumbers their male one, and the bounce rate here is much smaller than opening pinterest.com to see a smorgasbord of recipes and pictures of clothing in sepia.
A lot of your other complaints (like expecting the 45 seconds to be a timer) appear to be intentionally dense: I don't mean that to disparage you, but I think your interpretation is quite different than the average person Pinterest is trying to entice (that is, one with an average amount of experience on the internet.)