To begin with, what krossposting. In simple terms – krossposting is broadcast to your main blog (thanks to the rss-tape), other services free blog hosting sites. What it gives you? I think a lot of: 1) References to the original blog, I understand, their value is not high, but still. 2) Additional readers. At each free blog hosting has its own audience, which will look at yours, krossposting, even if not all of these people will go to your main blog, you’ll still get readers! Not on the main blog, so at some LJ. 3) Stand-alone service, and blogs on Blogger (blogspot), one devoid of useful features – buddylist (find friends) to participate in communities, clubs, or in some other way to develop your own profile. This could easily be offset by other services, and thereby further increase their audience, make friends, well, etc.
4) If a sudden something happens to the main blog you will have at least a few copies. 5) You can significantly increase their earnings by selling links, guards, sponsorship or other advertising space on krosspostinge. This is certainly not possible in all cases, and sometimes even problematic but services such as J2J, Blogun, if you want to use the can. With banner advertising things worse, but it can be put into each post. In any case, krossposting, it is at least a good argument for advertiser on your main blog.