Is the purpose to add flavor, moisture, or both?
Do you really think it makes a difference?
I generally put garlic, rosemary, and thyme in the pan for a roast. As the meat juices and butter flow into the pan, they make a wonderful infusion of flavour that is well worth bathing the roast in. I'm all for it - I feel the roasts I've made and basted are better than the ones I didn't baste. That said, I haven't done any double-blind studies.
This article claims both, as well as giving it an "attractive appearance." However, there are alternatives to basting that achieve this.
I don't ever recall my mum basting a beef roast. Instead she sears the outsides using a couple methods. Sometimes she'll toss it around in some hot oil in a dutch oven to lightly brown the outsides, then roast it (this proved to be messy, which may be why she switched to the next method). Other times she'll brown it in the oven using the broiler for 15-20 minutes and then switch to the bottom burner to roast it.
The lesson learned here:
QUICKLY cooking the outside of a piece of meat is the most effective way to lock in ("enhance") flavour and moisture. Then slow cooking for tenderness and texture to finish the job.
I don't believe basting is as effective. In essence, basting is like you're trying to put something back inside the meat. Why not keep it in there to begin with?
EDIT: My mom also occasionally uses a blow torch to sear a roast as well. She's a special lady.