According to TechCrunch, Foursquare is now attracting more than one million check-ins/week. It’s certainly a big number but does it really suggest that Foursquare is showing signs of becoming the next Twitter, or to be fair, the next widely-embraced social media tool?

Take look at Foursquare’s traffic over the past six months:

What’s interesting is that traffic growth in December vs. November was modest (unique visitors grew by 7.8%, while pageviews rose 15%). This is nice growth but not red-hot, which suggests Foursquare likely has a small group of enthusiastic users who account for a major chunk of traffic.

The big unknown is how much growth and traffic is coming from the popular iPhone app given Foursquare is a mobile service. There may be many users who have never touched the Web site other than to perhaps register for the service.

Still, I’m far less bullish and TechCrunch and ReadWriteWeb about Foursquare’s growth. There’s no doubt Foursquare has been enthusiastically embraced but it’s left to be seen whether it can break out beyond the bleeding edge. A big key will be if Foursquare can offer more services to keep people engaged once the novelty of “checking-in” begins to wear off.