As the venture business has grown and matured, many firms have developed specific areas of focus. Our firm, Union Square Ventures, for example only invests in web services. I believe this is a good thing for both the investors in venture funds, called LPs, and the entrepreneurs.

But there are a number of ways that firms can execute their focus on a particular area. Two of the most popular are "thematic investing" and "thesis driven investing".

They are very different.

Thematic investing involves identifying big themes and going after them. Examples from the world of web services would be "social networking", "online video", "ad networks", "social media", "real time", "mobile". I know many VCs who go about it this way. They identify the themes and then get busy filling out their portfolio with companies that fit those themes.

Thesis driven investing involves drawing a picture of where your particular area of focus is going. I like to take a five to ten year view. And once you have mapped out that picture, it becomes your thesis. And you evaluate every investment