It's a well understood and useful concept. Let's say you work at a job making $120K. Then in November, you start a new job paying $180K. Would you think that you make $130K (the amount you actually earned that year) or $180K (the amount you expect to make going forward)? Is the extra $50K fabricated salary?

How else would you communicate fast growth in revenue? Also, since run rate is well understood, people don't use it for exceptional or one-time events like a bonus. For example, Groupon didn't claim to be raising money at $12B/yr since the big raise was a one-time event.