Way old thread but it shows up in the forum list and I'm a vegetarian so what the hell?
As such, I am often amused at the way some non-vegetarians (i.e. 'normal' people) throw out the 'we are meant to eat meat' line whenever any questions about vegetarianism come up. The amusing part is not that the person in question is just parroting a line, but that they are doing so in an almost defensive way.
Let's be clear, though - I have no problems at all with meat-eaters. My long-time partner is not vegetarian and none of my previous partners have been. My family isn't vegetarian and none of my friends or co-workers are. I don't care if you use the 'meat tongs' to turn my vegetarian sausages on the BBQ. If I ever had kids, I would feed them meat until such time as they can make their own decisions.
My opinions as regards manufactured meat, therefore, are not based at all on an ideological position.
My first point would be, then, that growing meat naturally - in (e.g.) cow form - takes a lot of resources. It takes land and water and feed and medical treatment and so on.
Unfortunately, there are situations where this is just not feasible, the most notable one looming somewhere over the horizon being space travel. The proposed Mars colonists are unlikely to be enjoying steak or bacon when they get there.
It is very worthwhile to look at developing these alternatives because with time they will become more refined - cheaper to produce (in cost, required space and ingredients) - and thus more viable. There may well come a time in the not-right-now-but-not-that-far-off-either future where our population has expanded to such an extent that 'real' meat has become a luxury that very few are able to afford.
It might sound like some bad dystopian sci-fi scenario but our population is increasing as our usable farming land is decreasing - we need food sources that are sustainable, plentiful, affordable and nutritious. Taste is important but that can come later.