Is dropbox suitable as centralised bazaar storage?

We have been running a number of projects using bazaar with a decentralised workflow and merging our trunks periodically by exchanging flash memory storage. We would like to move to using a 'decentralised with shared mainline' model.

We would use launchpad, except we do not want to indiscriminately share our data and we do not wish to pay to keep it private. We would use a web server except we do not have the skills to set it up, nor have any of our friends have either the knowledge or server software compatible with bazaar. As you might have gathered we are self taught in the ways of version control, so our knowledge and competence is rather patchy.

Dropbox would seem to be a contender as an alternative to launchpad or another server space, but I think there may be fundamental reasons why it will not be reliable when there is more that one member in the team. But I don't really know how these things work, hence this inquiry. Perhaps as there are no forum posts warning of such problems my concrens are unfounded.

We have put a few projects on Dropbox (no trees) , and so far, so long as we pause Dropbox's syncing while bazaar is working on the repositories they are working fine.

Dropbox I think only tracks file by file whether there is a conflict, and if there is give you the choice 'keep yours' or 'keep theirs'.
Sooner or later if there is more than one team member you can be sure that two people will commit or push or pull to the master trunk on dropbox. My concern is that bazaar will allow both team members to access the repositories at the same time, and if by chance different component files in the repository are updated simultaneously, neither dropbox nor bazaar will detect the conflict, and this will scramble the repository.

Either this, or two or more team members pausing syncing of dropbox and pushing or merging or whatever, and then resuming syncing, and dropbox will interleave amended repository files, or unhelpfully say 'these 15 repository files are conflicted, tell me which ones you want to keep'. Either way it would seem the central master trunk will be toast.

Are these valid concerns? Or am i just thinking too much?