If there are only two major parties it is almost inevitable that one of them will get more seats than the other one and all the other minor parties combined and form a majority government.
If there are three or more major parties it is almost inevitable that none of them will get an overall majority.
With many people who might previously have seen a Lib Dem vote as a wasted vote now seeing them as worth voting for at last, and assuming Labour don't drift away to become a minor party, it looks like we could see a roughly equal three way split in any future election.
Does that mean we will always have coalition government, along with the bizarre situation of the party who comes third being the only one which is virtually guaranteed to be part of that coalition as they choose which of the other two to join ?