ASICMINER at IPO seemed a good opportunity to me.  At the time my fund was tiny - and GLBSE happened to close when our holding of it were low.  But it was the first (and only for about 6 months) share that I intentionally purchased as a long-term holding.  That decision is documented in my thread back then.  The 2nd such investment was DMC - a totally shite investment but it became worth holding due to its own holdings of ASICMINER after ASICMINER did well.  We actually made more from DMC than from ASICMINER itself.

On the bet you linked the Yes side is actually a great bet - not because there's any likelihood of BBET becoming massive this year but because there's a not insignificant chance of an S.DICE collapse.  i.e. the bet can be won by S.DICE losing market cap to below BBET as well as by BBET gaining market cap to above S.DICE.  I'd still favour the No side but for two factors:

1.  With the current odds of about 1:3 I'd be taking on CP risk and the risk of losing the bet in return for tieing up capital for 6 months for a 30% profit.  That's just totally unattractive.
2.  If MPEx were ever to delist S.DICE they MIGHT declare a win for Yes - as immediately after delisting they could argue S.DICE had a market cap of 0 (not being present in any market it wouldn't have a market cap - even if that were only temorary pending relisting elsewhere).  With MPEx/BBET run by same people there's conflicts of interest there I wouldn't want to go near (on the No side).  S.DICE is almost certainly in breach of its contract - by charging operational expenses to investors (when the contract explicitly limits what can be charged to expenses for promotion and development) - so delisting is far from impossible.

Whether ASICMINER's worth its current value or not is open for debate.  My take on it is to look at what income you believe is sutainable for it then work out what share price would be warranted with a similar P/E ratio to S.DICE or S.MPOE.