Join another program to take advantage of bonuses? You bet.
I do most of my flying on the West Coast, mostly on Alaska. But I had to take a trip to Houston last October. I wanted to fly non-stop on CO, and could have put the trip on my AS account for 3748 mi. But with the double-miles bonus last fall, plus a couple of promotions that I found out about from the Continental FT board, I was able to get 14,000 miles for the trip. Now that was an easy decision. I don't know what I'll do with my CO miles yet, but if I need to top off my Hilton account or get an intra-Hawaii flight, I'll use those rather than tap one of my higher balances in other programs.