This is absolutely what's going to happen if such system is implemented.
Appearing to delegate one way, but having their votes counted another way? Seriously? It is way too complicated for an average voter. Even if you implement some sort of plausible deniability scheme (so that aforesaid someone can't just login with your credentials and set it up the way they want) - imagine explaining plausible deniability to a 90-years-old grandma or some uneducated farm worker, or a drug addict...
Elections are rigged this way even in countries with supposedly secret votes: bad guys might ask you to prove your vote by, say, snapping a picture of "correctly" filled ballot alongside your ID, but even that is not necessary - enough people will do what someone with power tells them to on a vague threat "if you try to fool us we will find out", or because it's a "patriotic" thing to do, or simply because they are told to and don't know better.
Not to mention that a huge number of people just couldn't care less. Half of population simply don't show up at the polls. How many of them will simply sell their right to vote for a token sum of money?
The current system is bad in many ways [1], but this proposal is even worse - way too much potential for abuse.
[1] Some reasons why - http://en.wikipedia.org/wiki/First-past-the-post_voting