Fact: In its simplest incarnation, a Fact (capital 'F') is an observance of something real. I always like to use the example, "George Washington was White." It's pretty dead-on accurate. You can get into a tizzy about whether or not White and Black accurately describe someone's ethnicity, or into demagoguery by espousing the point of view that race should not be observable and that you're only propagating bigotry by reducing someone to the color of their skin, but let's be honest. GW was White.
In more complicated incarnations, a fact can be a little more difficult to ascertain. A more modern, relevant example of this would be the statement, "Cigarette smoke is not detrimental to your health." Is this a fact? Yes. What kind of fact? A False Fact. False Facts are observable statements that are typically relevant to a time-period. Fifty years ago, it was thought that cigarette smoke was not detrimental to someone's health. Our ability to observe it as such was not possible. A thousand years ago, the "Earth is Flat" was a Fact. Over time, our ability to observe real instances improves, so some Facts become false. They still remain, however, Facts, in an abstract sense because they are easily provable (or disprovable).
Opinion: Opinions, in essence, are a subjective interpretation of a Fact or set of Facts that can neither be proved or disproved. Personal values, experiences and future goals are huge factors in the formation of opinions. True Opinions cannot really be 'wrong', though sometimes anecdotal evidence can severely skew someone's perception of a Fact(s).
If True Opinions cannot be 'wrong' can an opinion ever be 'not right'? Yes. If an opinion is based upon False Facts, then it is not really an Opinion. It is a False Opinion. "George Washington was the greatest astronaut ever," besides being non-sequitur has no basis in reality. It's not a real Opinion. "I bet GW would have been a great astronaut," however, is a completely valid Opinion because one would assume that the statement would be based upon Facts relating to GW's ability to command a crew, leadership abilities, love of country, etc.
So, let's look at a very recent political issue and see if it passes Fact/Opinion rationality:
e.g.: The recent Healthcare Reform Bill passed by Congress is bad for America.
The keyword that demonstrates this as 'opinion' is the word 'bad,' which by nature is a subjective interpretation. To determine the validity of this statement as an Opinion or a False-Opinion, one would need to delve into what elements someone chose to form that opinion. Some Facts that would make this a True Opinion:
1) The US Gov has never attempted a social program of this magnitude before.
2) The US Gov has never had an individual mandate of any private product before.
3) Subsidizing Doctor's educations would increase supply of Doctors; thus, driving down the cost of medical services.
4) Healthcare is not expressly mentioned in the Constitution.
The above four Facts, which are observable (though, since the third is an extension of an economic argument, there is the potential of it later being proved a false fact) would lead someone to a valid Opinion that "Healthcare is bad for America."
If this opinion was based on facts such as the following:
1) The Healthcare Reform Bill is going to raise individual income taxes by 3,000%.
2) The HRB is going to round up Seniors in front of a Death Panel and euthanise them.
3) The HRB was signed into law by a President who was born in Kenya; thus, it is invalid.
4) The majority of Americans don't want healthcare legislated by the government.
If the above opinion was based upon any of the previous four 'facts' then it is a False Opinion and should be discounted.
Thesis: While Opinions can never truly be 'wrong', it is possible for an opinion to never have existed in the first place, if it never had a Fact to grow on.
