It's great to see that the Core developers chimed in, but I believe they may have underestimated the game theory that goes into why a UASF will drive a MASF, perhaps to their own benefit. No one wants a BIP 148, but we still might *need* it; I'd rather have miners and mining pools run by people that understand the importance of second layer solutions and generally support both the users and developers who want to see scarce cryptographic money replace fiat money in everyday aspects of everyone's life. It's okay if the developers maybe appear to have not understood the game theory behind BIP 148, they are, after all, more concerned about technicals and less concerned about the nature of man.
It only takes three reasonably equivalent miners/pools along with a decent base of users to make a UASF "work" when it comes to the raw game theory of BIP 148. At that point, all other miners/pools will have to consider the consequences of a UASF that sticks around and has an already activated SegWit running on it. Do big blockers and the agents that pay them behind the scenes to essentially attack Bitcoin really think no one else has been working behind the scenes to ensure at least two mining pools/groups are going to be switching over to it or offering a chance to mine on the new fork? And what of the spam attacks? Do they think that they are the only ones who can play that game?
I'm not even privy to all the details of what could happen, but I *definitely* understand the game theory aspects. It's far more advantageous for some of these larger mining pools to lie to each other about their opinions on the UASF while being ready to jump to it the second it goes live. A UASF gives them the ultimate way to screw over their competition. They'd be fools not to at least consider it and be ready.
Did any of you talk to Tycho when Deepbit was beseeched by Gavin to adopt BIP16? I did. He was the owner of the largest mining pool at the time (at ~30%) and was concerned about the consequences of trying to strong arm other miners into following him. He wasn't even sure if the technicals of BIP 16 were ones that users wanted, and he was terrified that choosing to move to it would risk forking the blockchain. At the time, I recommended he be opposed to what I called "developer hubris", though that designation was reserved specifically for Gavin after he added a line to his signature on the forums asking users to tell Deepbit to adopt BIP 16. I wrote this as a result of Tycho and I's conversations. To make a longer story short, the biggest mining pool can't ever signal their intentions or else they risk being on the wrong side of a fork by miners opposed to them. Since they can't signal their intentions, they need smaller pools to make their decisions for them.
We have yet to see the results of a UASF when there is miner hubris, but I suspect it won't be what you might initially expect would happen. Indeed, the only losers on August 1st could be the mining pools not ready for BIP148, because if three nearly insignificant mining pools decide they are going to support it and become the major players in a new fork of Bitcoin that has better features and a significant user base, then the core developers might be presented with a hard-to-pass-up opportunity to also agree to commit to the new fork with users that support them and miners that do as well. At that point, the only incentive for other small and mid-sized mining pools might be to determine if they really want to play second fiddle to the biggest mining pool and a developer base who have signaled support for making their fork of Bitcoin essentially a private coin for datacenters and governments to run.
If you guys want to know what's really going on behind the scenes, you should be asking these core developers if they would consider developing for a UASF BIP 148 chain assuming some semblance of it succeeds. If they all say never, then maybe there's nothing really going on and I'm just weak on game theory and SWOT analysis for smaller miners and pools. If any number of the developers say they would, however, then you're going to have to keep questioning if UASF BIP 148 is really all that bad or not. Sure, they reject BIP 148 as a good solution now, but they have to reject it in favor of status quo in all outside appearances, at least, for now. But if they won't rule out eventually someday developing code for a BIP 148 fork, then that rejection is only a formal one that belies what could be their real intentions.
I'm 100% in favor of a UASF because I want SegWit now. I would not be surprised if at least 3 mining pools also want it, regardless of what they are signalling right now. Even to their own employers/investors/friends/etc.