Boston residents open their homes after bombings

In a breathtaking display of generosity and trust, thousands of Bostonians are offering to take in marathon runners and visitors after today's explosions. Some are even students, although at least two at MIT had to withdraw their offers. "I was just told by the housemaster that we are not allowed to offer spaces for security reasons," one wrote.

By our count, 4,000-plus Boston-area households had offered their homes between about 5:30 and 8:30 p.m. ET, using an online Google form widely publicized on Twitter and Facebook. Our count doesn't include individuals who have made offers directly on Twitter under #BostonHelp and other hashtags.

As moving as these offers are, we urge good Samaritans to be careful about what information you submit through the Google form. The form feeds into a publicly accessible spreadsheet and exposes all of the personal information you provide. In some cases we've seen, people have offered not only their names, phone numbers, email addresses and neighborhoods, but even the number of people who live in the home and their schedules ("I work late but can be home quickly").

Appallingly, scammers prey on events like this, and msnNOW has reported that fake Boston charities have already surfaced on Twitter.

Our hearts go out to you, Boston.