Lewis Bush wrote an essay about corporate sponsorship and photography prizes. While there certainly are things to be said, I thought I'd briefly outline how I approach this whole complex. So in no particular order:
I have acted as a nominator for various prizes. In all those years, I have never been approached with the request to nominate specific people (or not to nominate others), whether in exchange for favours (or cold hard cash) or not. Needless to say, this could just be because I'm not smart enough to ask for such favours (who knows?).
I have not acted on the jury of a major corporate prize, but I'm tempted to assume that juries are not being influenced by corporate sponsors. Anyone claiming they are better have concrete evidence. Everything else - for me - simply is a conspiracy theory (and, just to add this, an attack on the integrity of the jury members).
As is always the case, I - just like everybody else I know (except for the jury members in question) - have always thought that the shortlist of this competition or the winner(s) of that competition should have been somebody else. That's what we boneheaded critics and people with opinions do. However, to infer from this that somehow the jury has to hide something (or to pursue some corporate agenda) is part of that conspiracy theory.
So essentially, for me to darkly hint at corporate interests (which, of course, exist, but which in the case of a prize might just be vastly different) or to hint at juries passively doing what their corporate paymasters want (let's ignore the fact that as far as I know juries aren't even paid for the work they do) does the discussion of the role of corporate money in the arts a disservice.
But that's just my 2 cents.