In physics, friction is a force that resists motion. In Microspeak, friction is an obstacle which prevents somebody from doing something you want them to do. (The preferred verb phrase for getting over an obstacle is overcoming friction.)

There is friction in the system for X that is reduced when developing with Y.
Using X reduces friction of someone being able to do Y without having to Z.
Many companies have found that outsourcing activities can introduce unexpected complexity, add cost and friction into the value chain, and require more senior management attention and deeper management skills than anticipated.
The goals of the Wiki include providing broader and more in-depth solutions content … from a wider variety of authors with less publishing friction than less traditional mechanisms.
While multi-tenancy and richer browser capabilities are valuable, I believe we have to start architecting multi-tenant solutions while incorporating the rich differentiation of new client platforms in disconnected and connected capabilities with the ability of ad-hoc collaborative communities forming around these services without centralized service friction.

(That last one deserves some sort of award for impenetrability.)

JD Meier kindly defines the term as it applies to communication:

It's obvious in retrospect, but I found a distinction between low-friction communication and high-friction communication. By low-friction, I mean *person A* doesn't have to work that hard for *person B* to get a point.

As the term friction gained popularity, second-order jargon emerged, such as friction-free (another citation).

(Remember that Microspeak covers not only terminology specific to Microsoft, but also business jargon that you need to know in order to "fit in.")