How can we tap the wisdom of micro crowds to influence the success of your online service or product?

I'm going to assume by micro-crowds you are really referring to niche targets. Niche targets can be divided up into a number of vertical subsegments which can probably be further divided and so on. I always thought traditional marketing segmentation was dubious at best. Trying to classify a consumer based on demographics and aspirations barely scratches the surface of an individual and makes rather erroneous conclusions about them just to be able to assign them into a box. Nowadays of course, you can let customers segment themselves. There are different ways to do this.

I'd start by taking an audit of the sentiment currently out there in the blogosphere, searching out any mention of the product or service...or even the the competition. Use technorati, see what's being tagged on del.icio.us or digg and what's ranking in Google or Yahoo.

After that, so far as your product has at least some reach you'll be able to identify and list a range of sentiment regarding your product and the environment or setting that sentiment is coming from. The nice thing about finding the said product in the social media world, is that you can almost zero in on the "micro crowd" by simply looking at the blog and its title. No guessing, just the observation of a natural enviroment where you can discretely interact without alerting other to the presence or a "analytical entity."