do you need a phd to be called a scientist

Not really, although it can help you to be taken more seriously if you are a professional scientist.

Nope! For me, people who are actively engaged in science (doing experiments, assisiting in research and, most importantly of all, publishing proper, peer-reviewed papers) are scientists. I know of high-school children who have published proper papers in science journals and for me, they are more of a scientist than a guy with a PhD who doesn't publish.

Sure, it really does help you a huge amount in get training and experience, but it's what you do rather than what you have that makes you a scientist.

Absolutely not - I work for a big research organisation and we have lots of professional scientists on the staff who don't have PhDs but provide fundamental roles in supporting reasearch as technical staff, providing very high quality support in particular specialized areas.  Many of these staff also sit on advisory panels, write scientific articles and papers and lead research projects in their own right.  They have usually got to their positions through alternative routes to the PhD but are no less professional and often vastly more competent at many of the technical aspects of running experiments than PhD graduates.

On a slightly different track, aside from the actual professional label, I think that "scientist" is actually a philosophical position as well, one that I embrace wholeheartedly. To be a scientist in this sense one only needs to subscribe to the central tenets of science and understand some basic concepts, like empiricism, peer review and the roles of theory and hypothesis. One certainly doesn't need a PhD for any of that:)

Etymologically speaking you could argue a philosopher is lover of knowledge (from the Greek) and a scientist is someone who knows (from the Latin). So being cheeky I'd say all scientists are philosophers, but not all philosophers are scientists.