Does anyone know why Google is treating a hyphen differently in search strings?

A hypen between two terms used to be really useful, in that it would return all possible versions of the two terms, as follows:

term1 term2 (i.e. with a space)
term1-term2 (i.e. with a hyphen)
term1term2 (i.e. with no space)

This is as described in the Google Guide, here:

http://www.googleguide.com/interpreting_queries.html

However, in the last few weeks this seems to have changed, both for normal Google searches and my Google Alerts (getting lots of irrelavent results which only contain one term)

Has anybody else noticed this strange behaviour?

It would be a real shame if Google has changed this very useful functionality!

Thanks,

Chris