Thanks to Marjorie Gavin for forwarding an email about this.
I hadn't heard of LostCousins before, which is odd in a way, as I'm in touch with very few of my cousins, so there are a lot of lost cousins out there.
The concept of the site is that you enter details of any ancestors and their siblings on the website, and if any two or more people enter the same person, they can be connected, and you'll find lost cousins. It covers only these censuses: England & Wales 1841, US 1880, Canada 1881, England & Wales 1881, Scotland 1881, England & Wales 1911, Ireland 1911, but they warn that their greatest coverage is of people in the 1881 census. They've chosen these censuses on the basis that most of them are available for free on the FamilySearch site, or can be accessed free at subscription sites.
Apparently the automated matching process is virtually 100% accurate, you won't waste your time corresponding with people who turn out not to be related - nor will you run the risk of allowing someone who is unrelated to have access to your family tree. What makes all this possible is that every LostCousins member is taking information from the same online censuses.
The accuracy of the matching process depends on the unique information about the census that you need to add for each person, the piece, book, folio, page
numbers from censuses in England & Wales; the volume (or registration number), enumeration district, page for Scottish censuses.
But there's the disadvantage, at least for me. I've found my ancestors and siblings on the censuses, taken a print of the info, but not all the information needed by LostCousins. For example, although I know that Robert Munro was in Belton Rd, Whitchurch on the 1901 census, it never occurred to me that it would be useful to write down the reference numbers; and it would be a pain to go through it all again. The second problem is that they want you to take the references from online censuses, whereas I researched my info from microfilms. Additionally, my ancestral families left Ireland before 1911, or arrived in the USA and Canada after 1900.
LostCousins is a great idea, however, I think that they haven't made it as user-friendly and usable as possible.
In their shoes, I'd have offered less accuracy without the census reference information, and/or after entry of a person's name, offered a list of census entries to select, and I've made these suggestions to them.
Perhaps you're think I'm making a mountain out of a molehill, or perhaps you think it would be worth searching the online censuses to get the required info.
If you do, or you have any other comments, please let me know by clicking the 'comments' link below.