I agree with Greg's 5% advice on making a NEW investment into a...

I agree with Greg's 5% advice on making a NEW investment into a speccie, as a general rule. If that 5% explodes then I will hold that even if it grows to a signifcant part of my portfolio. You do have to risk a bit to get rich... but you can offset that against multiple companies that are more likely to succeed than fail. I learnt a lesson last year...

I bought up 0.4% of a small biotech mid last year, in hindisght I think it was 2 years too early. Price has gone down and the money is well and truly locked up now.