Run rate is about quantities, not rates. If you made $10 in Jan, $40 in July, and $160 in the next Jan, then your run rate would be $1920, (12 x $160), not projecting 4x growth per 6 months forward.
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.
It doesn't communicate growth -- there is nothing to compare against. If you were going to do that, you'd simply provide a something like YOY% change in revenue.
A run rate is just inflating/fabricating PAST revenue by speculating on the FUTURE. Refer to my helpful chart:
| / <- SHOW THIS NUMBER TO INVESTORS, PRETEND IT WILL GO ON FOREVER
| /
|/ <- HIDE THIS NUMBER, TOO LOW
+---
