I believe mostly people who missed the train on the 19th July (I didn't, sold at 99 the day before).
If the buying whale makes another move today, up to 98 I believe, we'll find out if the sellers
get exhausted or not. If they do, the way to 100 and beyond is open IMO.
Don't be too preoccupied with the idea that only one entity in the world is accumulating bitcoins now, whereas the sellers are many. This is the age when the pros make their moves, and they don't necessarily use the exchanges at all, except for the purpose of price suppression. Bitcoin is quickly redeeming its place among gold and silver.
But there's so much resistance.. What makes you so bullish? Are you thinking we going over 100?
Volume is so small it does not matter much. The exchanges have their regulatory problems and worries, very few are willing to commit serious amounts of coin to Mt.Gox any more. This has changed over the last 3 months. I used to keep more than 2000 coins in Gox but do not do any more.
My bullishness is based on fundamentals. Bitcoin will be either destroyed, or become a dud, flourish, or conquer the world. The latter 3 scenarios all mean that price will increase compared to now. I have parked my bitcoins in deep storage - to be activated when the price hits $1400.
The risk is great but that can be mitigated by only investing what you can afford to lose. For many people that is quite much, actually