You could definitely just copy someone elses files (so long as they are the same bdb version, os, etc), but the problem is that you don't know if they are valid. You are trusting someone else.

A bootstrap gives you the entire blockchain, and then your client scans through the rules for the entire chain and indexes it. This is safe. The other way can work I have done it with a copy and paste of blkindex.dat blk0001.dat and database folder), but its not as safe.