well, you have to think in this way. ME2 was very successful and had very high review scores when it first came out on PC/360. Anyone who is really interested in this game should have already played it on PC or 360. I, for one, played the game on PC. It was a great game, I don't think any serious gamer that is remotely interested in this genre can resist it for a whole year just waiting for the PS3 version. Let alone the PS3 version was not announced till late last year.
So will I buy this game on PS3 again? Maybe.. the comic section is interesting and i can play with different startup choices in less than 15 minutes. But on full price? never.
So who are those 100K copies sold to? I believe they are new PS3 owners, who bought their first HD consoles last year and are interested in shooter RPG genre, PLUS hard-core ME2 fans who are willing to pay the full price to re-experience the game with upgraded graphics :)
So, nothing to worry about ME2 sales. it's expected. The fact that stores ordered such small number of copies at launch tells how much sales the industry really expected.