It's boards, not number of pins that seem to matter. I looked at the top 10 most-followed Pinners, and they were a diverse group. Some with over 1,000,000 followers. Men, women, and not just those involved with founding the site but (a few) seemingly random folks. Most people follow individual boards not other Pinners, so those with super-high numbers of followers are kind of rare.
Although they all had a zillion followers, they didn't have a lot of pins, relatively. But they had a lot of boards. And they boards they have are very specialized. People care about the quality of only a few niche pins instead of a lot of low-quality pins that are broad in nature such as "home". That shouldn't be too surprising, although if you look around Pinterest, there are a lot of "Home" boards.
However,be patient. The process of gaining loyal followers should be organic, which ultimately takes time. These tips should speed things along, though.
If you are on Twitter or a webmaster, you no doubt know the timing of your posts is very important. The same goes for pins. Be thoughtful and don't clog the boards with 100 pins of 1930's toilets at 8:00am or you will lose followers. What you DO want to do is dazzle influencers at critical times of the day. In marketing, this is known as Placement.
Be picky about what you pin(high-quality) and market yourself, your boards(niches) and your pins across the internet, such as on Wizzley (You can see/follow my pins at http://pinterest.com/musgrove/, for example ). Install the "pin It" Bookmarklet and pin original content. Introduce high-impact Pins from elsewhere, rather than repinning others's pins. Be sure to share interesting, focused and relevant video as well as static images.
Before you just start pinning everything you see, be judicious and empathetic towards your audience. Look and think about what you're pinning and how you present your pin. Remember most of the people on Pinterest are women, and (this comment may spur controversy) it's often treated as a place to fantasize about "womanly" things. I will leave that open to interpretation, but look at the pins that get the most action. Babies, home decor, diets (and total indulgence), wedding ideas, shirtless men, and so on. Cater to your audience and you will see an increase in followers.
Consider how you "come across." Are you presenting yourself as a sort or resource? A copycat? Then you need credibility. Think about your caption for each pin. Remember the phrase that a picture is worth a 1000 words. Unless you are just pinning something as a quick reminder or Ralph Lauren or Conan OBrien, it's usually best to let the photo do the talking when it comes to prosaic narrative. On the other hand, "Love" "Must Have" and a string of acronyms don't help other pinners find your pins and boards.
However, think keywords. What would and are people searching for? Label your pins with that and move on. Speaking of "searching for" it's not a bad idea to see what's trending as well. Again...find an audience and cater to them. They will follow you and spread the word to their followers.
Reciprocate. If someone like your pins, see if you want to like or follow any of their boards back. After all, everyone likes a compliment, which is what it amounts to. Like everything in life, the more you give, the more you get.
Above all, be interesting! Remember: you are competing for people's attention in real-time with everyone else on Pinterest and the web. Is what you are about to pin really THAT amazing? Has it already been pinned a bilion times (Like gotye's Somebody I Used to Know") and you just don't know it yet?