I have just looked at an ESL site that used to have a lot of free English language handouts and printables for teachers that has now started charging for access to the same worksheets. It seems somehow false pretences to offer a free selection and then impose a charge to see the same worksheets.
There is a real problem as sites that are successful cost a fortune in bandwidth and this needs to be paid for. However, it seems a bit draconian to me to suddenly impose a charge to access something that had been completely free before. As I see it, a free element should be included in order to ensure people that the product is worth buying. It also seems unfair to suddenly change from an entirely free site to one that charges.
There is definitely a case for paying for internet access as a successful site can cost a lot, and revenue from adverts may well not pay the costs involved, but changing from completely free to charging for access seems a rather unpleasant strategy to me. Without free access areas, how does the prospective consumer judge the quality of the goods on offer? Whatever is free on the UsingEnglish site, will always remain free.