2. Strange coalitions. At the federal level, we could very well be governed by a coalition including a Quebec separatist party. In other countries, it's not uncommon for extremes of the left and right to join up against the centrist party. (For example, in Ireland.)
3. The election of fringe party MPs. I'm not talking about more NDP and a few Greens, but single-interest and extremist candidates.
4. Loss of local focus. Instead of our current small ridings where we know the issues and can meet the candidates, we will be voting in much larger ridings and have much less understanding of the candidates or the issues. Depending on what form of PR is in place, there may not even be the concept of a local representative.
5. More instability in governance. With the creation of temporary alliances to form coalition governments, there will be greater swings in policy approach. It will be more difficult for the government to have a strong vision.
6. Undemocratic. Coalitions are created between members of the political elite, without any input from voters. Nobody voted for the coalition. A party that got few votes can wield a disproportionate amount of power.
I decided that proportional representation wasn't a great idea back in the late 1970s when I wrote an undergraduate PoliSci paper about it. I was motivated to jot down this list because lately in Canada all you hear is the advantages of PR over our current first-past-the-post electoral system. I agree that in the current system it's not fair that the NDP gets a way higher percentage of the popular vote than is reflected in the number of MPs they get elected. But we need to think through the downsides of changing our electoral system. As some famous guy said, Canada's political system works, except in theory.