1) Anyone who believes an xp cost in return for power/ability will dislike LA-buyoff and Bloodlines. Spells with an xp cost and player-made magic items (which require xp) seem to be more generally accepted due to the higher cost/benefit ratio.
(This is a perfectly valid philosophy which I find myself agreeing with more and more, in the interest of maintaining game balance.)
I'm derailing a bit, but I could argue fairly convincingly for the opposite view; that XP is not a fair cost for an increase in power or ability. This is because A) the drawback isn't immediate (you can't spend enough XP to lose a level in most cases, so you lose nothing in the very short term) and B) the drawback isn't permanent (you gain XP faster whenever you're actually paying for your power boost, which is whenever you're behind a level). This means there's a very specific window of when it's NOT a good idea to spend XP for more power; usually, when the power boost is only temporary (such as some spells with an XP component), and when your campaign is likely to run for only a few levels (and, incidentally, if you don't get XP in big chunks; if your DM tends to throw a single huge encounter a day at you, you're likely to consistently jump past level breaks along with your party, despite trailing a few hundred to a few thousand points). Otherwise, you get power now for a cost you only MIGHT pay later, and which eventually balances out to no cost at all (while you still might have the power).
Anyways, bloodlines are extremely confusing, and many attributes are highly arguable (especially because a lot of very important terms are either not defined anywhere, or only defined in extremely obscure places). For instance, SOME prestige classes which advance casting get their benefit doubled from bloodline levels, but some don't. You need to check the Spellcasting ability to see if it says something like, "At each level of this class..." or if it says, "At levels X, Y, and Z...". The first case gets awesomesauce, the second gets nothing. Note that ACTUAL spellcasting classes get no benefit, because they all gain their spells AT specific levels, rather than from a formula BASED on their level.