Note to online vendors:
I don't want to have to create an account to give you business.
Got it? By all means offer me the option of doing so, if that makes you happy, but if I'm buying 10 quid of lightbulbs from your site, or a one-off rail ticket, I really don't want to create a username and password, opt out of your effing mailing list, etc., etc. Imagine if you had to "create an account" with every corner store you bought £10 of stuff from.
And I really don't want to be prevented from making subsequent purchases because I can't remember the stoopid password I gave the last time you made me create an account I didn't want and your "reset your password" feature is slow/broken.
The relevant term here is "barrier to sale." If you're trying to sell things, here's a hint:
Barrier to Sale = Bad Thing(tm).
(Are you listening, National Rail?)