gmcbay
There is no conspiracy and I don't see what conversation needs to be had in this area. If you build a great game that runs on the 360 and is likely to sell a lot of units and differentiate the 360 in some significant way, Microsoft will be very interested in publishing your game on XBLA because doing so is in their best interest. That's all there is to it.
Just go into it with the mindset that getting on XBLA is like getting into the big leagues of pro sports, as far as casual game publishing goes. Many will try, very few will ever reach that level, no matter how much time and effort they devote. If you've never developed a commercially successful game before, the chance of breaking through is very small. You mention Microsoft doing something to make people "feel secure that investing effort won't be lost". They can't do that. 99% of small/casual indie games for any platform end as unpublished failures with all effort being "lost" (though for people who are really dedicated, I wouldn't say the effort is truly lost, nothing teaches as effectively as failure).
Until you have a great game built, you have nothing, so why should Microsoft or any other big publisher waste any time dealing with you or the 100,000 other people who think they are going to create the Next Big Thing They simply don't have the resources. That's life. If you want to hedge your bets, and you should, target both the PC and the 360 so if your game is rejected by Microsoft for XBLA publishing you can at least publish it to the PC shareware indie market.