Editor’s note: Legendary investor Vinod Khosla is the founder of Khosla Ventures. You can follow him on Twitter at @vkhosla. All Khosla Ventures investments, as well as ventures related to Vinod Khosla, are italicized.

We are in a whole new world of platforms, a post-PC era, which I’d more aptly describe as the always/everywhere era, finally, and that means a whole new set of opportunities. Add to it the fact that because of a variety of factors too numerous to cover here, the cost of experimentation has gone down dramatically (one can start a web startup or write an Android app with no more than a student credit card!) and raw computing power is taken for granted.

What you get as a result are the recent successes in the Internet/mobile space like Facebook, Twitter, LinkedIn, Zynga, Groupon and others, all of which have reenergized both entrepreneurs and investors. Many of these new startups will be the usual poor clones or feature add-ons to Facebook and Twitter, or poor attempts at doing one feature or another better than Zynga, or applying LinkedIn to a small vertical.

A few will be successful, many will fail, some will be acquired for a piece of technology or for the team (acqui-hires). But that does leave the question: What else new has the potential (nothing is certain!) to be truly disruptive or establish a new category in the domain of consumer Internet/mobile/services (which to me are fast becoming interchangeable)?

The post-PC always/everywhere platform will be defined by the many variations of mobile, always available, silent complementary standbys (like home or personal networks and agents) and more. A new category to me means doing something old differently enough to have it become a large business or have substantial impact among users.

AirBnB and Instagram would be examples of companies whose categories existed prior to their entry, but they are